3
a) has worked, since
b) have listened, for
c) hasn't studied, since
d) haven't written, since
4
a) were
b) moved
c) has had
d) finished
5
a) am
b) arrived
c) have been
d) am spending
e) left
f) finished
g) is
h) have designed
i) haven't learnt
j) is
k) has just sent
l) are having