1-non

2-la durée

3-devenu has been qui combien le present de l'auxiliaire HAVE et le participe passe de BE

4-une situation/ activite en cours

5- for two months

6- si on parle de durée on emploie FOR

si on indique le moment precis on emploie SINCE

7-FOR three days

SINCE monday

FOR two hours

SINCE three o'clock

SINCE the war

SINCE 2008

8-a-he is reading

b-he has been reading for five minutes

c-she is sleeping

d-she has been sleeping since breakfast