What does skylight mean?

[Ceo Neeraj]

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #49 "Up in the Clouds", question 6

You can see the sun if you look at the roof through the sky..........

(a) space
(b) light
(c) opening
(d) window

English Language Proficiency Tests, Advanced Level

ESL/EFL Test #49 "Up in the Clouds", answer 6

You can see the sun if you look at the roof through the skylight.

Correct answer: (b) light

Your answer was: incorrect
You can see the sun if you look at the roof through the skywindow.
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Hi,
What is skylight?
Is it the opening in the car's roof or is it a general term for any opening that enables you to see the sky??

HELP!!

[Mister Micawber]

.
A skylight is a window in the ceiling and roof of a building. In a car, it is a sunroof.
.
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Native English teacher at Mister Micawber's

[Thameem]

I used skywindow instead of skylight, could you please explain to me why skylight is a better option than skywindow?