Question

はやし

1、4、5、9、12番の文法問題についてです。
答えを見ても分からないので解説して頂きたいです🥲
ちなみに答えは、1から順に1、3、2、4、4です。

She (attends
attends to 3 attends on
attends in ) school regularly.
2. I hadn't seen Emi for years, but I ( reminded 2 realized 3 recognized 4 recovered) her at once.
3. "Why is this letter still here?" "Oh, no! I (D must've 2 should've © have ◊ had) posted it yesterday".
4. It is only natural that he ( could would 3 should might) complain about the treatment.
5.By the time she get 2 gets 3 getting 4 will get ) there, it will be nearly dark.
6. We suggested that he (D stops to drink 2 had to stop to drink stop drinking must stop drinking).
7. I have once lived lived 3 had lived have been living) here for three years when I was a child.
8. E-mail nowadays has become a new (1 mass matter means media) of communication.
9. You've done a good work 2 trade 3 occupation job).
10. ( We are necessary
11. This river is dangerous to (1 swim it
12 He mentioned a book (D which title
It is necessary that 3 It is necessary for us We are in need) to read them.
swim in 3 swim in it
swimming) in July.
with the title which 3 in which the title 4 the title of which)
I can't remember now.