3 they had visited
4 with whom
5 删掉 them
6 which 删掉
7 who 改成which ,同位语从句
8 which 改成that ,因为有the most
9 of 改成to
10 has 改成have ,因为前面是复数
11 on 改成in
12 which 前面加in
13 that 改成which
14 去掉the
15 第二个who改成that
16 there 改成with
17 look 改成looks
18 knows改成know
19 what 改成that
20 that改成which