题目内容：

根据句意，用括号内所给单词的适当形式填空

1.This book is the ________________ (结果) of 25 years of studying.

2.Mary received many presents, but she only _______________ (接受) three of them.

3.Simon is helpful, he often enjoys________________ (提供) help for others.

4.Don’t worry. Nobody is ________________(完美的) in the world.