I'm coming into this late, but...
In early language drills like this, teachers generally prefer full sentence responses to one word responses. (At any rate, it's more polite.) In other words, sentences with verbs.
my bad!! heh, kind of funny how once you get use to casual you kind of do not even want to use the more polite forms.
You wouldn't imagin how many times I was marked wrong for not using the
in my japanese 4 class >_<
teacher wanted that polite form in there.