大学英语：在主从复合句中，从句动词的时态取决于主句动词的时态

39.在主从复合句中，从句动词的时态取决于主句动词的时态。一般来说，主句动词为现在时，从句动词的时态则根据从句动词和主句动词所表示的动作先后次序来确定。

Many people believe that morning exercises do them a lot of good.

He thinks that it will rain tomorrow.

We know that we have missed an opportunity and that it may never come again.

I am in good shape because I used to do a lot of exercises.

He says that they are working on a new model of Boeing(波音飞机).

当主句动词为现在完成时时，从句动词一般为过去时。

Scientists have studied the universe ever since telescope was invented.40.若主句动词为过去时，从句动词一般为过去时或过去完成时，情态动词也要相应地改成过去时。引导间接引语的动词是过去时态时，也要用时态呼应的规则

Centuries ago,people held a belief that the sun moved around the earth.

He thought that it would rain the next day.

若主句动词为过去完成时，从句动词一般用过去时。

He had done all that was necessary.

By the time they found the hacker,he had already broken into the computer system of the bank.

在使用过去时态呼应规则时，应注意过去时态只与过去的事件有关，与现在的情况无关。

I got the job because I was a good driver.(并不表示我现在就不是好司机)

I wanted to join the police,but I wasn’t tall enough.(不表示我现在就高了)