Give correct form or tense of the verb

Giải dùm mình câu này. Nhanh dùm mình với
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III. Give correct form or tense of the verb.
9 16. A lot of trees (blow).
17. As far as I know, she (not come) hasn't come back yet.
18. He (send) had sent
blew
down in the storm last night:
me a very nice letter a few days ago. X
19. John wishes he (have) _ had
20. How much time do you spend (surf) _surf
a mountain bike. /
the web a day?