1 . _________ environmental damage is done, it takes many years for the ecosystem to recover.

A．Even if

B．If only

C．While

D．Once

2 . —Have you known each other for long?
—Not very long, ________ we started to work in the company.

A．after

B．before

C．when

D．since

3 . Nancy enjoyed herself so much ______ she visited her friends in Sydney last year.

A．that

B．which

C．when

D．where

4 . I thought him nice and honest   ______I met her

A．first time	B．for the first time
C．the first time	D．by the first time

5 . Only ________ as a translator ________ how important it is to understand foreign cultures.

A．when did I work; I realized	B．when I worked; I realized
C．when did I work; did I realize	D．when I worked; did I realize

6 . Some scientists believe that it won’t be long _______ robots are widely used in all walks of life．

A．since

B．after

C．before

D．until

7 . When _____ the letter, tears came to her eyes.

A．she was reading

B．reading

C．she reading

D．read

8 . ________ a child begins school, he enters a world of fierce competition where success and failure are clearly defined and measured.

A．Before

B．Until

C．Whenever

D．The moment

9 . How long do you think it will be ________ the computer company brings out a new product?

A．until

B．when

C．before

D．that

10 . It was        Asimov was eleven years old        his talent for writing became obvious.

A．that, when	B．When, that
C．when, when	D．when, which