请问宾语从句什么情况下只能用WHETHER不能用IF

什么是宾语从句

一、宾语从句中的时态。 1。如果主句的时态是一般现在时或一般将来时，从句的时态则根据具体情况或具体意义来确定。如： ① I don't know when he came back。 ② Do you know where they will go this summer holiday? ③He is worried about whether he has passed the English exam。 ④ Please tell us what we should do next, OK? ⑤ Will you please tell me how I can get to...全部

  一、宾语从句中的时态。 1。如果主句的时态是一般现在时或一般将来时，从句的时态则根据具体情况或具体意义来确定。如： ① I don't know when he came back。
   ② Do you know where they will go this summer holiday? ③He is worried about whether he has passed the English exam。
   ④ Please tell us what we should do next, OK? ⑤ Will you please tell me how I can get to the post office? 2。
  如果主句的时态是一般过去时，从句的时态则相应地使用一般过去时/过去将来时/过去完成时/过去进行时等。如： ① He said that he didn't find your lost pen。
   ② My parents told me that they would go to Beijing。 ③ The policeman asked him what he was doing at midnight yesterday。
   ④ I told you yesterday that I had returned your book。 Why do you ask for it again? 3。如果宾语从句所叙述的是客观真理、自然现象、名言警句或谚语等，不管主句是什么时态，从句都用原时态。
  如： ① Our geography teacher told us that the earth goes around the sun。 ② When I was young, my father often told me that knowledge is power (力量)。
   二、宾语从句前通常需要有引导词。 1。 如果宾语从句是由陈述句转变而来的，其引导词用that，常可以省略。如： I hope (that) I can study English better。
   2。 如果宾语从句是由一般疑问句转变而来的，其引导词使用if / whether, 意为"是否"。 如： Mr Chen asked , "Are you all here?"→Mr Chen asked if / whether we were all here。
   3。 如果宾语从句是由特殊疑问句转变而来的，其引导词使用连接代词what / which /who / whose 或 连接副词when / where / why / how 等。
  这些连接词都要充当从句中的一个成分，故不能省略。如： Tom asked me， "When did you begin to study English?" →Tom asked me when I began to study English。
   上面的回答了，那我就告诉你一些类型吧~ 。收起