1.
A
rather than
B
to
C
than
D
rather
2.
existed not
did not exist
had not existed
have not existed
3.
to stay
stay
stayed
have stayed
4.
wake
woken
waking
to wake
5.
had woken
woke
has woken
6.
7.
to read
reading
read
have read
8.
watch
to watch
watched
watching
9.
10.
had
have
to have
have had
11.
done
do
did
to do
12.
help
helped
to help
helping
13.
delayed
have delayed
delay
would delay
14.
does
have done
15.
16.
to feel
feeling
felt
feel
17.
were
to be
be
being
18.
having
19.
doing