The Congo river: tigerfish, the deepest river, lungfish and hidden birds

Tests: 3 of 12 right · Exam: 1 of 4 right · Kind: plain · Understood: 10 of 16 · Run: 2026-10-18, commit f3c23ea72

Lesson 160 of the biology course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: the lesson in the corpora.

Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: the lesson's questions in the corpora.

Test 1 · right ✓

In a cartoon, Gloria the hippo swims gracefully in a pool. What is true of real hippos?

1. They swim like dolphins — no support
2. They float on top of the water all day long, like big grey logs — no support
3. They never go into water — no support
4. They cannot really swim; they walk and bounce along the bottom — ← Mova's choice · ✓ the right answer · score 8

Why: It took the question to ask which statement is true. It chose option 4 with score 8, the only option with support. Its support: lesson 102, line 6: «Hippos cannot really swim; they are so heavy that they sink, so they walk or bounce along the bottom and push up to breathe.», reached through the same lesson line as the sentence the question matched. What matched: the same action «bounce» (+5); the same place «bottom» (+3). · the question and its options parsed, with trees and pragmatics

Test 2 · right ✓

«that hippo's bleeding all over, is it hurt??» What is the best answer?

1. Yes, a crocodile bit it — no support
2. Probably not; it makes a red oily fluid that works like sunscreen — ← Mova's choice · ✓ the right answer · score 11
3. It is red mud only — no support
4. Yes, hippos always bleed through their skin when they stay out in the sun too long — score 5

Why: It took the question to ask what it is done to. It chose option 2 with score 11, against 5 for the next best. Its support: lesson 102, line 7: «Hippos ooze a red-orange liquid sometimes called «blood sweat», which is neither blood nor sweat but works as sunscreen and may help stop germs in cuts.», reached through the option's own match among the sentences about the question's things. What matched: the same circumstance (+5); the same action «work» (+4); a different doer (counts against) (+2). · the question and its options parsed, with trees and pragmatics

Test 3 · wrong ✗

A fisherman shows a fish with big teeth and says it is part shark. What is it most likely?

1. A mix of a shark and a pike, born in the river — no support
2. A goliath tigerfish, which only looks sharky — ✓ the right answer · no support
3. A real shark that swam up into the river from the sea — ← Mova's choice · score 8
4. A baby whale that lost its way far up the river — no support

Why: It took the question to ask which statement is true. It chose option 3 with score 8, the only option with support. Its support: lesson 134, line 3: «Down in the black deep sea a real anglerfish dangles a glowing lure lit by bacteria, and any small fish that swims up to the light ends up behind teeth that po…», reached through the same lesson line as the sentence the question matched. What matched: the same action «swim up» (+5); the same doer «small fish» (+3). The right option, 2, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 4 · right ✓

A tigerfish leaps at a bird skimming over the water. Why can that work?

1. It hunts fast and has long teeth that trap prey — ← Mova's choice · ✓ the right answer · score 8
2. It shoots a jet of water at the bird to knock it down — score -1
3. It can leap out and fly for a few metres above the water — score 6
4. It is not a fish at all but a bird that dives into the river — no support

Why: It took the question to ask why something happens (its cause). It chose option 1 with score 8, against 6 for the next best. Its support: lesson 160, line 5: «The goliath tigerfish is one of the fiercest river fish, with long teeth that stick out like a crocodile's, and hunts in the fast rough water of the Congo.», reached through the same lesson line as the sentence the question matched. What matched: the same action «hunt» (+4); the same doer «goliath tigerfish» (+2); the same property (+2). · the question and its options parsed, with trees and pragmatics

Test 5 · wrong ✗

3 hippos walk along the riverbed. How many ears and how many tails?

1. 6 ears and 6 tails — ← Mova's choice · no support
2. 3 ears and 6 tails — no support
3. 12 ears and 3 tails — no support
4. 6 ears and 3 tails — ✓ the right answer · no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 6 · wrong ✗

A dwarf crocodile and 2 forest buffalo stand near a swamp. How many legs and horns?

1. 8 legs and 2 horns — ← Mova's choice · no support
2. 10 legs and 4 horns — no support
3. 12 legs and 4 horns — ✓ the right answer · no support
4. 12 legs and 6 horns — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 7 · wrong ✗

«found a mud ball, gonna smash it» Why might that be a bad idea in the Congo?

1. Mud is poisonous to touch — ← Mova's choice · no support
2. It might be a bird's nest made of gold, hidden there long ago — no support
3. It could hold a lungfish waiting for the rain — ✓ the right answer · no support
4. Mud balls explode — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 8 · wrong ✗

What would happen if the elephantnose fish's electricity stopped working?

1. It would see better — no support
2. Nothing would change — no support
3. It would see much better without the electric field to confuse it — ← Mova's choice · score 3
4. It could not sense its way or other fish in the dark water — ✓ the right answer · score 2

Why: It took the question to ask what happens next. It chose option 3 with score 3, against 2 for the next best. Its support: lesson 160, line 3: «In the murky water an elephantnose fish cannot see, so it makes weak electricity and feels the world by its electric field, and in dried-up pools a lungfish sl…», reached through what followed the sentence the question matched. What matched: the same circumstance (+4). Against it: a different doer (counts against) (-1). The right option, 4, scored 2. · the question and its options parsed, with trees and pragmatics

Test 9 · wrong ✗

«kingfishers eat fish, it's in the name, innit» What is right?

1. Kingfishers eat only seeds — score 5
2. Yes, every kingfisher in the world eats only fish and nothing else — score 5
3. Kingfishers are a kind of fish — ← Mova's choice · score 6
4. Not always; the pygmy kingfisher mostly snatches insects — ✓ the right answer · score 6

Why: It took the question to ask which statement is true. It chose option 3 with score 6, tied with another option at 6 (the first shown, or the one claiming less beyond what it knows, wins). Its support: lesson 160, line 18: «African pygmy kingfishers are tiny kingfishers that mostly hunt insects in woods, not fish in rivers.», reached through the same lesson line as the sentence the question matched. What matched: the same doer «tiny kingfishers» (+3); the same circumstance (+3). The right option, 4, scored 6. · the question and its options parsed, with trees and pragmatics

Test 10 · wrong ✗

«why's no one ever seen that peacock thing» Why is the Congo peafowl so rarely seen?

1. It is shy and lives only deep in the Congo forest — ✓ the right answer · no support
2. It lives underground in burrows and only comes up at night to feed — ← Mova's choice · score 0
3. It only comes out once a year — no support
4. It is extinct — no support

Why: It took the question to ask why something happens (its cause). It chose option 2 with score 0, the only option with support. Its support: lesson 1, line 1: «A habitat is the place where a living thing lives and finds everything it needs: the right air or water, food, shelter and a safe place to raise its young.», reached through the option's own match among the sentences about the question's things. The right option, 1, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 11 · wrong ✗

A loud honking fills the forest at night. What is a likely source?

1. A lungfish in its mud ball — ← Mova's choice · no support
2. A hippo snoring — no support
3. Male hammer-headed bats calling to females — ✓ the right answer · no support
4. Leopards purring — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 12 · wrong ✗

Why can scientists not reach the bottom of the deepest parts of the Congo with a pole?

1. Tigerfish bite the poles — no support
2. The bottom of the river is made of soft mud that swallows the poles — ← Mova's choice · score -1
3. The water flows uphill — no support
4. The river is more than two hundred metres deep there — ✓ the right answer · no support

Why: It took the question to ask why something happens (its cause). It chose option 2 with score -1, the only option with support. Its support: lesson 88, line 9: «Geckos stick to glass with millions of tiny toe hairs that cling by very weak attractions between molecules, and scientists have made tape that copies them.», reached through the option's own match among the sentences about the question's things. Against it: a different thing acted on (counts against) (-1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · wrong ✗

Select the response consistent with the established facts concerning the depth of the Congo River.

1. Its depth does not exceed two metres at any point — ← Mova's choice · no support
2. It is the shallowest of the great rivers of Africa — no support
3. Certain sections exceed two hundred metres in depth, rendering it the deepest river known — ✓ the right answer · no support
4. Its depth has been established as approximately two kilometres, exceeding that of most seas — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · wrong ✗

Identify the principal means by which the elephantnose fish perceives its surroundings in turbid water.

1. Vision of exceptional acuity in darkness — ← Mova's choice · no support
2. The emission of high-pitched calls and the detection of their echoes from the riverbed — no support
3. Contact with the riverbed by means of its fins — no support
4. The generation of weak electric fields and the detection of their alteration — ✓ the right answer · no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · right ✓

Which of the following statements most accurately characterises the conduct of the African lungfish during drought?

1. It ascends into the trees until the rains resume — no support
2. It encases itself in mud and a cocoon of slime and breathes air until the return of rain — ← Mova's choice · ✓ the right answer · score 2
3. It migrates overland to the nearest permanent river, travelling by night upon its fins — no support
4. It perishes upon the evaporation of the water — no support

Why: It took the question to ask who or what does it. It chose option 2 with score 2, the only option with support. Its support: lesson 160, line 13: «African lungfish dig into mud when the water dries up, wrap themselves in a slime cocoon and breathe air through a small hole until the rains come, sometimes f…», reached through the option's own match among the sentences about the question's things. What matched: the same action «breathe» (+3). Against it: a different doer (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Exam question 4 · formal language · wrong ✗

Ascertain the reason for which the hippopotamus progresses along the riverbed rather than swimming.

1. Its great weight causes it to sink, and it is unable to swim in the proper sense — ✓ the right answer · no support
2. It pursues fish upon the riverbed — no support
3. It is pursued upon the surface by crocodiles — ← Mova's choice · score 3
4. It avoids the warmth of the surface water and remains in the cool mud at all times — no support

Why: It took the question to ask which statement is true. It chose option 3 with score 3, the only option with support. Its support: lesson 73, line 9: «Whales are mammals whose ancestors walked on land about 50 million years ago; their back legs shrank to small hidden bones, and their closest living land relat…», reached through the option's own match among the sentences about the question's things. What matched: the same thing acted on «hippopotamus» (+3). The right option, 1, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/biology/160-the-congo-river/