Ответ:

I

1 becomes

2 are exploding

3 cut...., was walking

4 have not reached

5 will go

6 had

7 has been working

8 had left

9 would volunteer

10 would have helped

11 more expensive

12 the biggest

13 не знаю.

III.

1 ACTIVITY

2 не знаю.

SHORTEN