1 . It is often the case ________ anything is possible for those who hang onto hopes. （用适当的词填空）

2 . _______ I experienced that day has become one of the most unforgettable memories.

3 . It’s still unknown_________ he’ll go abroad for further study or not.

4 . It suddenly occurred to him _____ he had left his keys in the office.

5 . ____________________________________ still remains a mystery.
恐龙为什么突然消失了还是个谜。

6 . ____________________________________ is of great importance.
他是否能按时完成任务非常重要。

7 . The limits of a person’s intelligence，generally speaking，are fixed at birth，but ____________________he reaches these limits will depend on his environment.

8 . 我们需要的是更多的水。
____________________________ is more water.

9 . 他为什么做这件事还不十分清楚。
__________________________________ wasn’t quite clear.

10 . 有人担心，洪水的结束将是另一场疾病的爆发。
It is feared ______________________________ the floods, another disease would ______________.