U1
1.in five years
2.fall in love with
3.keep a pet
4.be able to do sth
5.come true
6.one of the+形容词最高级+可数名词复数：最...的之一
7.in the future
8.help with sth
9.hundreds of
10.make sb. do sth.
11.orer and over again
12.get bored/be bored/feel bored
13.look for
14.seem possible
15.in college
16.on weekends/on the weekend
U2
1.pay for sth
2.borrow sth. from sb.
3.ask sb. for sth
4.buy sth.for sb.
5.argue with sb.
6.find out
7.get of well with sb.
8.have a fight with sb.
9.out of style
10.in style
11.as..as possible
12.complain about sth.
13.compare A with B
14.on the one hand,...on the other hand...
U3
1.in front of
2.get out of
3.take off
4.have a/an experience
5.on a tree
6.in a tree
7.think about doing
8.for example
9.hear about
10.in silence
11.take place
12.in history
13.in space