就是在主句时态为“非现在时”时和“非将来时”时，
从句的时态必须与主句相呼应。（现代语法家一般将时态分为“过去时”和“非过去时”）。
原意
英语中的时态呼应(the sequence of tenses)就是在主句时态为“非现在时”时和“非将来时”时，
从句的时态必须与主句相呼应。（现代语法家一般将时态分为“过去时”和“非过去时”）。其规则如下：
规则
1.主句谓语为现在时或者将来时态，
从句中的谓语时态可以不受影响，即按照意思决定时态。如：
It is reported that they are building a new railway.
Will you please tell us how you got to knwo it?
2.如果主句谓语为过去时，则
从句谓语的时态要做相应改变。
I don't know where they live.
I didn't know where they lived.
He wants to know how you're doing.
He wanted to know how you were doing.
I wonder if they have got a reply.
I wondered if they had got a reply.
I know you have been worrying about us.
I knew you had been worrying about us.
I hope she will find a job soon.
I hoped she would find a job soon.
I think she will be playing golf this time on Sunday.
I thought she would be playing golf this time on Sunday.
I expect he will have changed his mind by tomorrow.
I expected he would have changed his mind by tomorrow.
She will have been teaching in this university for 20 years by this summer.
She told me that she would have been teaching in this university for 20 years by this summer.