过去进行时

• 形式：was/were ding
• 用法： she was reading a book at 11:00 last night
• 否定疑问： she was not reading a book
• 补充：一件事情持续进行，另一件事情突然出现把他打断。
  -- while you were sleeping，a thief sneaked in
  -- while i was cooking yesterday，a friend locked at the door

短语补充

• try to do sth ：尽力做某事（第10课、13课都有用到）
• try doing sth ：决心没那么强烈

过去完成时

• 现在完成时：have/has done
• 过去完成形式：had done
• 用法：过去的之前，站在过去的时间点，回头看过去发生的事情
• before 8:00 yesterday，she had finished her homework
• 否定疑问：had not done
• 补充：过去完成/现在完成时区别
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