单词拼写。根据句意和首字母或汉语提示，将单词的正确形式写在题中相应的横线上。

1. O_________ cover more than 70 percent of the earth's surface.

2. Could you please speak more s__________, Tom? I can't catch what you say.

3. __________ (数以百万计的) of people around the world cannot get clean water.

4. A scientist says that beautiful music can make cows __________ (生产) more milk.

5. Paris has some fantastic sights, __________ (包括) the Eiffel Tower and Notre Cathedral.