1, walk -> was walking
2, eats -> had eaten
3, phoned -> had phoned
4, has -> had
5, were -> were being
6, has disappeared ->disappeared
7,was cooking -> cooked
8, saw -> have seen
9, graduates -> had graduated
10, had -> have had
11, was cooking -> cooked
12, catching ->was catching
13, buys -> bought
14, is looking -> looked
15, was sat -> sat
16, turned -> were turning
17, really needed -> had really needed
18, since-> for
19, have -> had
20, listenintently. -> listening