用括号内所给单词的适当形式填空。

1. —How big are the manatees?

    —They're about on      __    (foot) long and 1, 000 pounds heavy.

2. It was       __   (discover) that pandas were endangered.

3.  —What are they doing?

     —"They are trying _______ (help) the environment.

4.  We should take our own bags when _______(shop).

5.  I was _______ (surprise) to see Jim at the party.  I thought he was in hospital.

6.  Visiting zoos are like to read _______ (live) textbooks for young people.

7.  Do you know what place is _______ (suit) for tigers to live in?

8.  The environment _______ (pollute) is more and more serious.

9.  My elder brother decided to go abroad to continue his _______ (educate).

10.  The Students' Union urges all the students       __     (stop) chewing gum.