Expressions: 'at night' vs. 'for night'

[Mick]

English Grammar Tests, Elementary Level

ESL/EFL Test #51 "English Grammar Exercise", question 9

Do you lock the front door ......... night?

(a) for
(b) at
(c) on
(d) from

English Grammar Tests, Elementary Level

ESL/EFL Test #51 "English Grammar Exercise", answer 9

Do you lock the front door at night?

Correct answer: (b) at
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right or wrong - expression: 'at night'

Mick

[Yankee]

.
Yes, "at night" is correct.

[Tae_Way]

why not for?

[NinaZara]

tae_way,

If you close a door, won't you be doing it for yourself/your own safety?Why would you want to close the door for "night"? Unless there's a person called "Night".
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Try your best and damn the rest.

[Conchita]

Welcome, Tae Way!

You could also lock the door for the night, though, meaning during the night.