小测验：选择正确的单词

1. The self-timer is sometimes very useful.
   有时候定时装置很有用。
2. In the short run this could be a very useful policy.
   短期看来这将是个非常有用的政策。
3. A foreign language is a useful tool.
   外语是有用的工具。
4. I am yearning to make myself useful.
   我想使自己成为有用的人。
5. Perhaps this book will prove useful later.
   也许这本书今后会有用。

　2个形容词解释