B1>
1.to
2.for
3.in
4.about
5.from
B2>
1.It's very important to keep the environment clean.
2.The time machine will be shown to the public when it is finish.
3.He was delighted that his aunt sent him a letter.
4.People recycle old car tires to make shoes and sandals.
5.I'm very sad not to be accepted in that group.
B3>
1.learning
2.are
3.of
4.you
5.how
6.book
7.fly
8.yourself
9.playing
10.practice