高悬赏！！帮我看看这几道英语怎么改错？？

The car that I bought it is very expensive. it去掉，定语从句the car做宾语，故it重复。
The girl who she is sitting next to Li Ming my cousin.who后面的she去掉，有先行词了，就不加she，重复。
Mary,we invited to our party,is going to study abroad.在we前加上who，定语从句缺宾语。
Do you konw Mike, his car was stolen the other night.将his改成whose，物主代词引导定语从句。
The man with who we talked in the street yesterday is our new teacher.将with调置talked后，固定短语不能分开。

The car that I bought is very expensive.
The girl who is sitting next to Li Ming is my cousin.
Mary,who we invited to our party,is going to study abroad.
Do you konw Mike, whose car was stolen the other night.
The man we talked with in the street yesterday is our new teacher.

1.that 改 which
2.把she去掉
3.We后面+ are
4.who改成 whose
5.Who 后面+that

(The car that I bought ,it is very expensive.之间应该有逗号吧?不然错两处了)

1*去掉it 2*去掉she 和第一题一样，不然主语过多
3*可能是去掉we 因为第二句已够成了一完整的话 4*把his改成whose 5*可能是把is改成was 好像是时态问题，不大肯定