Ex. 1.
to hear -heard - heard
to think - thought - thought
to build - built - built
to take - took - taken
to fly - flew - flown
ex. 2.
1. after, 2. back, 3. round, 4. in, 5 forward.
ex. 3.
1. is plauing
2. are not sleeping
3. write
4. do you listen
5. are you playing
ex. 4.
1. were playing 2. answered, 3. were you doing 4. began 5. didn't go, was writing
ex. 5.
1. will not take, 2. returns, will call, 3. comes, will spend, 4. will you do, 5. will pass
ex. 6.
1. has been cooking
2. have you ever performed
3. have been known
4. has just returned
5. has she already chopped