時態(tài)一致

1) 如果從句所敘述的為真理或不變的事實(shí)，則永遠(yuǎn)用現(xiàn)在時。 At that time, people did not know that the earth moves. He told me last week that he is eighteen.

2) 賓語從句中的助動詞ought, need, must, dare 時態(tài)是不變的。 He thought that I need not tell you the truth.