1 . 阅读下面短文，在空白处填入 1个适当的单词或括号内单词的正确形式。

The giant panda     1     (love) by people throughout the world. Chinese scientists     2     (recent) had a chance to study a wild female panda with a newborn baby. She was a very     3    (care) mother. For 25days, she never left her baby, not even to find something     4     (eat)! She would not let any other pandas come near. She licked the baby constantly to keep it clean. Any smell might attract natural     5    (enemy) that would try to eat the little comforting panda. The mother held the baby in her front paws much the way a human does.     6     it cried, she rocked it back and forth and gave it little comforting pats. The mother continued to care for the young panda     7     more than two years. By that time, the panda no longer needed     8    (it) mother for food. However, it stayed with her and learned about the ways of the forest. Then, after two and a half years, the mother     9     (drive) the young panda away. It was time for her to have a new baby,     10     it was also time for the young panda to be independent.

2 . We share the resources of the world, ______ any action of waste can affect other people.

A．so

B．if

C．unless

D．because

3 . There’s no way of knowing why one man makes an important discovery ________ another man, also intelligent, fails.

A．since

B．if

C．as

D．while

4 . Good news never goes beyond the gate, ______ bad news spreads far and wide.

A．when

B．as

C．while

D．before