---
title: Identify the principal cause of the blue colour of the daytime sky. — Mirrors, rainbows and the blue sky · tree and pragmatics
description: Identify the principal cause of the blue colour of the daytime sky. Exam question 1 of lesson 21 «Mirrors, rainbows and the blue sky» of the physics course of Mova's primary school, with the dependency tree and pragmatics of the question and of each option; Mova's choice was wrong.
---

<!-- md -->
[Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/questions/physics/21-mirrors-rainbows-and-the-blue-sky/e1/)

<!-- crumbs -->
[home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [questions](https://md.mova.elamur.ai/free/en/corpora/questions/) / [Physics](https://md.mova.elamur.ai/free/en/corpora/questions/physics/) / [Mirrors, rainbows and the blue sky](https://md.mova.elamur.ai/free/en/corpora/questions/physics/21-mirrors-rainbows-and-the-blue-sky/) / e1

# Exam question 1 · Mirrors, rainbows and the blue sky

<!-- .ven lang=en -->
Identify the principal cause of the blue colour of the daytime sky.

<!-- .vintro -->
**Mova's choice:** option 1 · **The right answer:** option 4 · wrong ✗ · **Who acts:** you · **What happens:** identify, cause · **To what, where:** principal cause, blue colour

<!-- .vabout -->
This is exam question 1 of lesson 21 «Mirrors, rainbows and the blue sky» of the physics course of Mova's primary school, asked in stiff, formal language. The page gives the question's syntax tree — a dependency tree in the style of Universal Dependencies — and its pragmatics clause by clause, then the 4 options as the student saw them, each with its tree and pragmatics. Every text is parsed by Mova itself. How the student answered it, with the score of every option and why: [the test at school](https://md.mova.elamur.ai/free/en/school-run/physics/21-mirrors-rainbows-and-the-blue-sky/#e1).

## The question {#question}

```conllu
# sent_id = question:physics:21-mirrors-rainbows-and-the-blue-sky:e1:1
# text = Identify the principal cause of the blue colour of the daytime sky.
1	Identify	identify	VERB	VB	Mood=Imp|VerbForm=Fin	0	root	_	_
2	the	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
3	principal	principal	ADJ	JJ	Degree=Pos	4	amod	_	_
4	cause	cause	NOUN	NN	Number=Sing	1	obj	_	_
5	of	of	ADP	IN	_	8	case	_	_
6	the	the	DET	DT	Definite=Def|PronType=Art	8	det	_	_
7	blue	blue	ADJ	JJ	Degree=Pos	8	amod	_	_
8	colour	colour	NOUN	NN	Number=Sing	4	nmod	_	_
9	of	of	ADP	IN	_	12	case	_	_
10	the	the	DET	DT	Definite=Def|PronType=Art	12	det	_	_
11	daytime	daytime	NOUN	NN	Number=Sing	12	compound	_	_
12	sky	sky	NOUN	NN	Number=Sing	8	nmod	_	SpaceAfter=No
13	.	.	PUNCT	.	_	1	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **identify** | imperative | you *not said here* | the principal cause of the blue colour of the daytime sky |  |  |  |  | vn characterize-29.2-1-1 «NP V NP S\_ING»: agent=Agent cause=Theme |
| 2 | **cause** |  |  | the blue colour of the daytime sky |  |  |  |  | nom cause «event transitive»: of=patient |

<!-- .note -->
One row per clause the reader finds. «not said here»: a role filled from the clause above. «roles by»: a VerbNet class and frame when one fits the verb, else the reader's rules on the tree.

## The options {#options}

### Option 1 · ← Mova's choice {#o1}

<!-- .ven lang=en -->
The emission of blue light alone by the Sun

```conllu
# sent_id = question:physics:21-mirrors-rainbows-and-the-blue-sky:e1:o1:1
# text = The emission of blue light alone by the Sun
1	The	the	DET	DT	Definite=Def|PronType=Art	2	det	_	_
2	emission	emission	NOUN	NN	Number=Sing	0	root	_	_
3	of	of	ADP	IN	_	5	case	_	_
4	blue	blue	ADJ	JJ	Degree=Pos	5	amod	_	_
5	light	light	NOUN	NN	Number=Sing	2	nmod	_	_
6	alone	alone	ADV	RB	_	5	advmod	_	_
7	by	by	ADP	IN	_	9	case	_	_
8	the	the	DET	DT	Definite=Def|PronType=Art	9	det	_	_
9	Sun	Sun	PROPN	NNP	Number=Sing	2	nmod	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **emit** |  | the Sun | blue light |  |  |  |  | nom emission «act transitive»: of=patient by=agent |

### Option 2 {#o2}

<!-- .ven lang=en -->
The reflection of the oceans upon the atmosphere

```conllu
# sent_id = question:physics:21-mirrors-rainbows-and-the-blue-sky:e1:o2:1
# text = The reflection of the oceans upon the atmosphere
1	The	the	DET	DT	Definite=Def|PronType=Art	2	det	_	_
2	reflection	reflection	NOUN	NN	Number=Sing	0	root	_	_
3	of	of	ADP	IN	_	5	case	_	_
4	the	the	DET	DT	Definite=Def|PronType=Art	5	det	_	_
5	oceans	ocean	NOUN	NNS	Number=Plur	2	nmod	_	_
6	upon	upon	ADP	IN	_	8	case	_	_
7	the	the	DET	DT	Definite=Def|PronType=Art	8	det	_	_
8	atmosphere	atmosphere	NOUN	NN	Number=Sing	2	nmod	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 3 {#o3}

<!-- .ven lang=en -->
The intrinsic blue colour of outer space

```conllu
# sent_id = question:physics:21-mirrors-rainbows-and-the-blue-sky:e1:o3:1
# text = The intrinsic blue colour of outer space
1	The	the	DET	DT	Definite=Def|PronType=Art	4	det	_	_
2	intrinsic	intrinsic	ADJ	JJ	Degree=Pos	4	amod	_	_
3	blue	blue	ADJ	JJ	Degree=Pos	4	amod	_	_
4	colour	colour	NOUN	NN	Number=Sing	0	root	_	_
5	of	of	ADP	IN	_	7	case	_	_
6	outer	outer	ADJ	JJ	Degree=Pos	7	amod	_	_
7	space	space	NOUN	NN	Number=Sing	4	nmod	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

### Option 4 · ✓ the right answer {#o4}

<!-- .ven lang=en -->
The preferential scattering of blue light by the gases of the atmosphere

```conllu
# sent_id = question:physics:21-mirrors-rainbows-and-the-blue-sky:e1:o4:1
# text = The preferential scattering of blue light by the gases of the atmosphere
1	The	the	DET	DT	Definite=Def|PronType=Art	3	det	_	_
2	preferential	preferential	ADJ	JJ	Degree=Pos	3	amod	_	_
3	scattering	scattering	NOUN	NN	Number=Sing	0	root	_	_
4	of	of	ADP	IN	_	6	case	_	_
5	blue	blue	ADJ	JJ	Degree=Pos	6	amod	_	_
6	light	light	NOUN	NN	Number=Sing	3	nmod	_	_
7	by	by	ADP	IN	_	9	case	_	_
8	the	the	DET	DT	Definite=Def|PronType=Art	9	det	_	_
9	gases	gas	NOUN	NNS	Number=Plur	3	nmod	_	_
10	of	of	ADP	IN	_	12	case	_	_
11	the	the	DET	DT	Definite=Def|PronType=Art	12	det	_	_
12	atmosphere	atmosphere	NOUN	NN	Number=Sing	9	nmod	_	_
```

<!-- .note -->
The frames reader finds no event or fact in this sentence.

<!-- div src -->

**Text:** the tests of Mova's primary school, written for Mova (`world/data/school/`), as the course runner gave them to the student. **Trees:** Mova's own parse — the `en` model on the CPU, when the site is built — not checked by a teacher; they may be wrong. **Frames:** Mova's frames reader (`prag`), each text read on its own. Elamur Cosmic License.

<!-- /div -->

<!-- pn -->
- ← previous: [Mirrors, rainbows and the blue sky, test 11](https://md.mova.elamur.ai/free/en/corpora/questions/physics/21-mirrors-rainbows-and-the-blue-sky/t11/)
- next →: [Mirrors, rainbows and the blue sky, exam 2](https://md.mova.elamur.ai/free/en/corpora/questions/physics/21-mirrors-rainbows-and-the-blue-sky/e2/)
- ↑ back to [Mirrors, rainbows and the blue sky](https://md.mova.elamur.ai/free/en/corpora/questions/physics/21-mirrors-rainbows-and-the-blue-sky/)