1 . ________ a significant number of jaguars survive here, they are only one element of this forest’s food chain. (用适当的词填空)

3 . Tom went to bed i________ (一…就，立即) he reached his home. (根据中英文提示单词拼写)

4 . —Some English idioms are difficult to understand.
—Exactly, ______ you know the meaning of each word.

A．if only

B．only if

C．as if

D．even if

5 . The government calls on us to avoid visiting crowded areas and medical institutions _______ it is necessary.

A．while

B．because

C．unless

D．when

6 . —I went to see you at about ten this morning, but you were not in the office.
—Oh, that was probably _______ I was talking with the headmaster.

A．when

B．why

C．what

D．that

7 . The girl was then hit a second time by another van _________ an elderly trash collector came to her aid, according to some witnesses.

A．before

B．where

C．until

D．when

8 . We don’t need magic to change the world____we carry all the power we need inside ourselves already: the power to imagine better, said J.K. Rowling.

A．though

B．unless

C．before

D．when

9 . ________ nobody gave him any help, he must have done the research on his own.

A．Now that	B．Although
C．Though	D．For

10 . Using renewable energy sources is a simple idea, but ________ we find it hard to put into practice.

A．one	B．what
C．which	D．that