题目内容：

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。

Happiness is like a small stone1. (drop) into a pool to cause a circle of ripples.2.  Stevenson has said, being happy is a duty. There is no exact definition of the word “happiness”. Happy people are happy3. all sorts of reasons. The key is not wealth or physical well-being, since we find4. (home) people, disabled people and so-called losers are extremely happy.

Being happy is a sort of unexpected gain. But staying happy is5. accomplishment, a   success of soul and character. Actually it is not selfish to strive for it. It is, indeed, a duty to ourselves and others.

Being unhappy is like an infectious disease. It causes people6. (stay) away from the  sufferer. He soon finds himself alone. There is, however, a cure for it: if you don’t feel happy, pretend to be.

It works. Before long you will find that instead of repelling people, you attract them. You will discover 7. deeply  rewarding it is to be the center of wider and wider circles of good will.   Then the make-believe becomes a8. (real). You become really happy.

Being happy,  once it is recognized as a duty and develops into a habit, 9. (open) doors   into amazing gardens which are full of10. (thank)friends.