复合句中的从句(主要指宾语从句)的时态要和主句的谓语动词保持时态上的一致，称为时态的呼应。要注意下列问题：
1)主句谓语动词是现在或将来时态时，从句的动词不受影响。
【例如】
It is reported that a new railway is going to be built there next year. Has he told you when he is to leave for Kunming?Will you tell us how you managed to overcome the difficulties?
2)主句谓语动词是过去时态，从句也必须使用过去时态。从句用过去进行时/一般过去时，表示主、从句的谓语动作同时发生；从句用过去将来时，表示从句的动作在主句动作之后发生；从句用过去完成时，表示从句的动作在主句动作之前发生。
【例如】
I didn t know you were already ahead of us.
She asked me whether I had passed the final examination.I thought you wereshavingsa break now.Did you say you had been waiting for us?I was thinking that you wouldn t be going with us.She said they would have got everything ready by tonight.They told me that Professor Li would have been teaching here for thirty years by this winter.
3)如果从句表示的是真理、客观事实，则一律用现在时，不受主句时态的影响。
【例如】
Even then, people knew that tides are caused by the moon.This proved once again that the earth is round.The teacher said that the Yellow River is the second largest river in China.