B.L.

例句：

1. 1.I don't know what happened to the computer, but it's not working properly.
   我不知道电脑发生了什么，但它现在不工作了。
2. 2.The meeting was postponed due to the sudden rain.
   由于突然下雨，会议被推迟了。
3. 3.The book is about a time when people lived in caves and didn't have electricity.
   这本书讲的是人们生活在洞穴里，没有电的时代。