时间状语从句和条件状语从句中的主将从现： 一般说来, 若主句的谓语动词表示将来的动作或存在的状态时, 与其 连用的时间或条件状语从句的谓语动词常用一般现在时表示将来时间. 这种用法常见于以下几种情况: 一. 当主句的谓语动词是一般将来时时, 由when, before, after, as soon as, until 等连词引导的时间状语从句和由if引导的条件状语从句用一般现在时. 例如: Well go to visit the Great Wall if it doesnt rain tomorrow. 如果明天不下雨, 我们将去参观长城. Ill tell him the good news as soon as I see him. 我一见到他, 就告诉他这个好消息. 二. 当主句的谓语含有may, can, must等情态动词时, 由when , before, after, until, as soon as等引导的时间状语从句和由if引导的条件状语从句用一般现在时. 例如: You may go fishing if youre free. 如果你有空, 你可以去钓鱼. You can go home after you finish your homework. 你做完作业后就可以回家. 三. 当主句的谓语是want, hope, wish等动词的一般现在形式, 由when, before, after, until, as soon as引导的时间状语从句和if引导的条件状语从句用一般现在时. He wants to be a doctor when he grows up. 他长大后想当一名医生. 四. 当主句是祈使句时, 由when, before, after, until等引导的时间状语从句和由if引导的条件状语从句用一般现在时. 例如: Look before you leap. (谚语)三思而后行. Put up your hands if you have any questions to ask.如果有问题要问, 请举手. 宾语从句的时态问题 1）当主句的谓语动词是一般现在时时，其宾语从句的时态可以是任何适当的时态。 所以，宾语从句的时态应根据实际情况而定。 She says (that) she works from Monday to Friday. 她说她从周一至周五上班。 （从句是一般现在时） She says (that) she will leave a message on his desk. 她说她要在他桌子上留个便条。 （从句是一般将来时） She says (that) she has never been to Mount Emei. 她说她从来没有去过峨嵋山。 （从句是现在完成时） 2）当主句的谓语动词的时态是一般过去时的时候， 其宾语从句的时态一般要用任一适当的过去时态。 He said there were no classes yesterday afternoon. 他说昨天下午没有课。 （从句是一般过去时） He said (that) he was going to take care of the baby. 他说他会去照看这个婴儿。 （从句是过去将来时） He said (that) they were having a meeting at that time. 他说他们那时正在开会。 （从句是过去进行时） 但是当宾语从句是表达客观真理和规律的句子时，其时态仍旧用一般现在时。 The teacher told us(that) nothing is difficult if we put our hearts into it. 老师告诉我们世上无难事,只怕有心人。 She said(that) her father is twenty-eight years older than her. 她说她父亲比她大二十八岁。 He said that light travels much faster than sound. 他说光比声音传播得快。 He told me that I must go to school on time every day. 他告诉我我必须每天按时上学。