I.
8, Does she play
9, will change
10, fell / was riding
11, is raining
12, came / was practicing
13, was attending
14, don't play
15, will call

II.
1, the slowest
2, more quickly
3, the best
4, more often
5, later
6, the most beatifully
7, easier
8, more simple
9, as slowly as
10, more carefully

III.
1, must
2, must
3, mustn't
4, must
5, has to
6, must
7, mustn't
8, mustn't
9, haven't to
10, mustn't

I.
1, are you studying
2, took
3, doesn't tidy
4, were sitting / saw
5, is coming
6, left
7, discovered / was taking
8, Does she play
9, changes
10, fell / was riding
11, was raining
12, came / was practicing
13, was attending
14, don't play
15, will call
ii
1, the slowest
2, more quickly
3, the best
4, more often
5, later
6, the most beatifully
7, easier
8, simpler
9, as slowly as
10, more carefully

IV.
1. not to make
2, leaving
3, to take
4, not touching
5, going
6, seeing
7, meeting
8, to join
9, to play
10, to see
11, doing
12, to go