III
1 lost
2 arrived
3 broke
4 has lived
5 left
6 stayed
7 always writes
8 did
9 has ... phoned
10 see ... saw
IV
1 learned / learnt
2 visited
3 cycled
4 have never tried
5 Have ... found

Baì 3:
1. have lost ( ở đây dùng quá khứ [lost] ko sai nhưng have lost sẽ chính xác hơn)
2. arrived
3. has broken ( câu she is still in the hospital là để nhấn mạnh sự tiếp diễn từ quá khứ đến hiện tại nhưng chưa kết thúc nên mình nghĩ thế này đúng hơn)
4. would live
5.left
6. stayed
7. always writes
8. did
9. Has/phoned
10. don't see /saw
Bài 4:
1.have learnt
2.visited
3. cycled
4. have never tried
5. Have/found