1. Many experts agree that once these treasures are _______ to the air, great harm will be done to them. So they think it better not to unearth the treasures.

A. exposed                   B. threatened

C. constructed                D.conserved

2. While watching television,__________.

A. the doorbell rang             B. the doorbell rings

C. we heard the doorbell ring     Dwe heard the door bell rings

3. ________, he knows a lot of things.

A. A child as he is              B. Child as he is

C. A child as is he              DChild as is he