4. it 形式主语
it+be动词+形容词+to do
D正确
be able to
it+be动词+表语
5.must have been done
对过去的一种被动语态的推测
must have done:对过去的一种推测
I'm sure I think
9.a large sum of money
A正确 amount of
an amount of+不可数(a large amount of)
plenty of
10.be going to打算，计划
want to
喜欢 I want it
Lesson 22
dream v.做梦，梦想
age n.年龄
channel n.海峡
throw v.扔，抛
have a dream
dream a dream
have a good dream
sweet
have a good /sweet dream