which one is better

[sage]

excuse me, which one is better? and why ? thanks^^

They hadn't done their homework last week

They didn't do assignment last week[/b]

[Casiopea]

excuse me, which one is better? and why ? thanks^^

They hadn't done their homework last week

They didn't do assignment last week[/b]

They didn't do the assigment last week. :D
They didn't do their homework last week. :D

The Perfect (i.e., have done, had done) isn't compatible with past time adverbials (i.e., last week[/i]).

All the best, :D