时态一致

 　　1) 如果从句所叙述的为真理或不变的事实，则永远用现在时。

　　At that time, people did not know that the earth moves.

　　He told me last week that he is eighteen.

　　2) 宾语从句中的助动词ought, need, must, dare¹ 时态是不变的。

　　He thought that I need not tell you the truth.

1 dare   

n.敢，挑战；aux.敢；vi.敢；vt.敢于，勇于面对

参考例句：

• He didn't dare to look at her in the face.他不敢正眼看她。
• How dare you?Take your hand off me at once.放肆！马上把你的手挪开。