Choose the right verb forms to complete the sentences.

Choose the correct option.

I [didn't buy|didn't bought|wasn't buy] any new clothes last year.

What [were you doing|did you doing|were you done] when I called?

I saw a boy who [has just been stopping|had just stopped|did just stop] playing tennis.

When I was twelve, I [have already studied|was already being studied|had already been studying] English for six years.

When I [knocked|did knock|knocking] on the door, it opened.