We use present perfect tense for the actions began in the past but never finished yet.

AFFIRMATIVE

S + have/ has + Past Participle
(V+ed/3rd form)

1. They have finished my
homework.

2. She has stopped
running.

3. You have done your
exercises.

4. He has bought a book.

NEGATIVE

S + haven’t /hasn’t + Past
Participle

1.They haven’t finished
my homework.

2.She hasn’t stopped
running.

3. You haven’t done your
exercises.

4. Ha hasn’t bought a
book.

INTERROGATIVE

Have/Has + S + Past Participle

1.Have they
finished your homework?

2.Has she stopped
running?

3. Have you done
your exercises?

4. Has he bought
a book?

FOR and SINCE
JUST, ALREADY, YET