语法总结
used to 与 be used to 的对比
前者写过去习惯，后者写现在已习惯，这是本课最经典语法点。
相似句：
- I used to live in Shanghai.
- I am used to living alone now.
when 表示“就在这时突然”
we were flying... when the plane suddenly turned round 让转折更有突发性。
相似句：
- I was walking home when it began to rain.
- She was speaking when the lights went out.
过去完成时被动
had been told / had been planted 用来交代返航前已经发生的安全警报。
相似句：
- We had been warned about the storm.
- The money had been hidden in the wall.