11.27 時態(tài)一致
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  1) 如果從句所敘述的為真理或不變的事實,則永遠用現(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.