---
title: An ambulance's siren drops in pitch as it drives away. Which sky clu… — How we know: measuring the sky · tree and pragmatics
description: An ambulance's siren drops in pitch as it drives away. Which sky clue works like that? Test 4 · ★★★ of lesson 28 «How we know: measuring the sky» of the space course of Mova's primary school, with the dependency tree and pragmatics of the question and of each option; Mova's choice was right.
---

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# Test 4 · ★★★ · How we know: measuring the sky

<!-- .ven lang=en -->
An ambulance's siren drops in pitch as it drives away. Which sky clue works like that?

<!-- .vintro -->
**Mova's choice:** option 3 · **The right answer:** option 3 · right ✓ · **Who acts:** siren, sky clue · **What happens:** drop, drive away, work · **To what, where:** pitch

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This is test 4 · ★★★ of lesson 28 «How we know: measuring the sky» of the space course of Mova's primary school. 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/space/28-how-we-know-measuring-the-sky/#t4).

## The question {#question}

<!-- .note -->
*Sentence 1:* An ambulance's siren drops in pitch as it drives away.

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:1
# text = An ambulance's siren drops in pitch as it drives away.
1	An	a	DET	DT	Definite=Ind|PronType=Art	2	det	_	_
2	ambulance	ambulance	NOUN	NN	Number=Sing	4	nmod:poss	_	SpaceAfter=No
3	's	's	PART	POS	_	2	case	_	_
4	siren	siren	NOUN	NN	Number=Sing	5	nsubj	_	_
5	drops	drop	VERB	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	0	root	_	_
6	in	in	ADP	IN	_	7	case	_	_
7	pitch	pitch	NOUN	NN	Number=Sing	5	obl	_	_
8	as	as	SCONJ	IN	_	10	mark	_	_
9	it	it	PRON	PRP	Case=Nom|Gender=Neut|Number=Sing|Person=3|PronType=Prs	10	nsubj	_	_
10	drives	drive	VERB	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	5	advcl	_	_
11	away	away	ADV	RB	_	10	advmod	_	SpaceAfter=No
12	.	.	PUNCT	.	_	5	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **drop** | present | a ambulance's siren |  |  | pitch |  |  | vn roll-51.3.1 «NP V PP.trajectory»: agent=Theme in pitch=Trajectory |
| 2 | **drive away** | present | siren |  |  |  |  | away *property* | vn nonvehicle-51.4.2-1 «NP V PP»: agent=Theme |

<!-- .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.

<!-- .note -->
*Sentence 2:* Which sky clue works like that?

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:2
# text = Which sky clue works like that?
1	Which	which	DET	WDT	PronType=Int	2	det	_	_
2	sky	sky	NOUN	NN	Number=Sing	3	compound	_	_
3	clue	clue	NOUN	NN	Number=Sing	4	nsubj	_	_
4	works	work	VERB	VBZ	Mood=Ind|Number=Sing|Person=3|Tense=Pres|VerbForm=Fin	0	root	_	_
5	like	like	ADP	IN	_	6	case	_	_
6	that	that	PRON	DT	Number=Sing|PronType=Dem	4	obl	_	SpaceAfter=No
7	?	?	PUNCT	.	_	4	punct	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **work** | present | sky clue |  |  |  |  | like that | vn employment-95.3 «NP V»: agent=Agent |

## The options {#options}

### Option 1 {#o1}

<!-- .ven lang=en -->
Parallax of a nearby star

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:o1:1
# text = Parallax of a nearby star
1	Parallax	parallax	NOUN	NN	Number=Sing	0	root	_	_
2	of	of	ADP	IN	_	5	case	_	_
3	a	a	DET	DT	Definite=Ind|PronType=Art	5	det	_	_
4	nearby	nearby	ADJ	JJ	Degree=Pos	5	amod	_	_
5	star	star	NOUN	NN	Number=Sing	1	nmod	_	_
```

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

### Option 2 {#o2}

<!-- .ven lang=en -->
The phases of Venus

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:o2:1
# text = The phases of Venus
1	The	the	DET	DT	Definite=Def|PronType=Art	2	det	_	_
2	phases	phase	NOUN	NNS	Number=Plur	0	root	_	_
3	of	of	ADP	IN	_	4	case	_	_
4	Venus	Venus	PROPN	NNP	Number=Sing	2	nmod	_	_
```

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

### Option 3 · ← Mova's choice · ✓ the right answer {#o3}

<!-- .ven lang=en -->
Redshift of a galaxy moving away

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:o3:1
# text = Redshift of a galaxy moving away
1	Redshift	redshift	NOUN	NN	Number=Sing	0	root	_	_
2	of	of	ADP	IN	_	4	case	_	_
3	a	a	DET	DT	Definite=Ind|PronType=Art	4	det	_	_
4	galaxy	galaxy	NOUN	NN	Number=Sing	1	nmod	_	_
5	moving	move	VERB	VBG	VerbForm=Ger	4	acl	_	_
6	away	away	ADV	RB	_	5	advmod	_	_
```

<!-- .fr -->
| # | verb | tense, mood | who | what, whom | to whom | where | when | other | roles by |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1 | **move away** | gerund | a galaxy *not said here* |  |  |  |  | away *property* | vn roll-51.3.1 «NP.theme V»: agent=Theme |

### Option 4 {#o4}

<!-- .ven lang=en -->
Dark lines of helium

```conllu
# sent_id = question:space:28-how-we-know-measuring-the-sky:t4:o4:1
# text = Dark lines of helium
1	Dark	dark	ADJ	JJ	Degree=Pos	2	amod	_	_
2	lines	line	NOUN	NNS	Number=Plur	0	root	_	_
3	of	of	ADP	IN	_	4	case	_	_
4	helium	helium	NOUN	NN	Number=Sing	2	nmod	_	_
```

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

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**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.

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- ← previous: [How we know: measuring the sky, test 3](https://md.mova.elamur.ai/free/en/corpora/questions/space/28-how-we-know-measuring-the-sky/t3/)
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