翻译句子。
1. The theory should _______________ (以事实为基础).
2. _____________ (在警察的帮助下), he found the lost child.
3. He works _______________ (如此努力以至于大家对他的评价很高).
4. _______________ (别灰心) when you are in trouble.
5. This was a time ______________ (当时这两个国家正在交战).