at night or that night

[Tyrion Lann]

Hello folks.

I got a sentence in my book " the class teacher gave him a home work & instructed him to do it at night."

I have to find a single error with that sentence. I know the obvious one is "a home work" but what about "at night". I think it should be "that night" . Shouldn't it?
Thanks.

 

[se16teddy]

Yes: "at night" means something like "not in daylight hours".