英语从句动词时态

可以存在主句是一般过去时，从句是现在完成时的情况的。原因如下：当从句表示客观事物或真理，或人们已经公认的道理时，其时态不受主句谓语动词的时态的影响。即使主句谓语动词使用了过去时的某种时态，从句的时态仍然是现在的某种时态。当然一般情况下，主句是一般过去时，从句一般也应该是过去时态的。一、在宾语从句中主句和从句之间的时态的一致关系，通常由主句谓语的时态决定从句谓语的时态。⒈若主句谓语动词是现在时或将来时，如：一般现在时，现在完成时，一般将来时，将来完成时等，从句可以根据需要使用任何时态。⒉若主句谓语动词是过去时态(一般过去时，过去进行时，过去完成时，过去将来时，过去将来完成时)，从句谓语动词也必须是过去时态。⑴如果从句动作与主句动作同时发生，从句用一般过去时或过去进行时。⑵当从句动作发生在主句动作之前，从句要用过去完成时。⑶当从句动作发生在主句动作之后，从句要用过去将来时。⒊当从句表示客观事物或真理，或人们已经公认的道理时，其时态不受主句谓语动词的时态的影响。即使主句谓语动词使用了过去时的某种时态，从句的时态仍然是现在的某种时态。⒋当从句表示并未出现或尚未实现的愿望时，必须用过去时态。⒌有些形容词后面可跟有从句，这种从句一般可看作宾语从句，其谓语也应与主句谓语的时态保持一致。可跟这种宾语从句的形容词有：afraid, glad, sure, confident, sorry, certain, conscious, aware等。一致的原则与宾语从句相同。例如：I'm confident that I'll pass the exam. 我有信心通过考试。He was lucky that he wasn't killed. 他很幸运没有被杀死。二、在主语从句，表语从句和同位语从句中，主句和从句之间的时态一致关系所遵守的法则和宾语从句相同。例如：It appears that some little trouble was caused by a woman, whose name has not been ascertained. 看来这件小小的麻烦是由一个至今尚不清楚其姓名的女人所引起的。It was known long ago that Professor Einstein played a key role in the development of the theory of relativity. 人们早已知道，爱因斯坦教授对相对论的发展起了关键作用。It was proved centuries ago that the speed of light is 186,000 miles a second. 几世纪前就证实了光的速度为每秒186,000英里。The fact that man would soon be able to visit the moon built up new scientific interest in earth's nearest neighbor. 人类不久可以游览月球的事实，引起了对地球最近邻居的新的科学兴趣。三、定语从句与主句的时态一致关系⒈若定语从句的谓语表示的动作和主句谓语表示的动作同时发生，则要求使用同样的时态。例如：The original manuscript of "The Theory of Relativity" was written by Einstein who was then an employee in a patent office. “相对论”的原稿是由当时在一家专利办公室工作的爱因斯坦写的。⒉主句与定语从句的谓语表示的动作如果不是同时发生，时态则不要求一致。例如：Have you seen the new golf clubs that Mr. Stevens gave Bill? 你看过史蒂文斯先生给比尔的那些新高尔夫球棒了吗？I painted several pictures that are now on show in the museums. 我画了几张画，现在正在博物馆里展出。四、状语从句与主句的时态一致关系⒈如果状语从句的谓语表示的动作和主句谓语表示的动作同时发生，则要求使用同样的时态。例如：Immanuel Kant was so regular in his habits that until the day he died people were able to set their watches by his actions. 伊迈努尔·康德的习惯那么有规律，以至直到他死以前人们都能按他的行动来对表。When Abraham Lincoln became President of the United States of America, he was completely involved in the problem of slavery.当亚伯拉罕·林肯成为美国总统时，他便陷入到奴隶问题的漩涡中去了。⒉由when, while, as引起的进行时，若主句表示的动作比从句表示的动作更引人注目，主句用过去时(或现在时)，从句用过去进行时或现在进行时)。若两个动作同样注目，可以都使用进行时。例如：As I was walking along Main Street, a car mounted the pavement and crashed into a shop. 当我正沿着大街走时，一辆汽车越过人行道，冲进一家店铺里去了。While the child was playing with his toys, his parents were reading books. 孩子在玩玩具，他父母在看书。When I was returning home from school, a parade of demonstrators walked along the streets. 当我从学校回家时，一队游行示威者从街上走过。⒊如果状语从句的谓语表示的动作和主句谓语表示的动作不是同时发生，则要使用相应的时态。注意：使用after与before连接的状语从句之间的区别在于：●使用after时，从句用完成时；使用before时，主句用完成时。●因为after与before两个连词本身已表示动作有先后，所以由这两个连词引起的状语从句也可以使用与主句一样的时态。例如：The director had explained the details many times before the workers took the job. 工头在工人们开始工作前把细节给他们讲了好多遍。Each of the major glacial stages produces distinctive land forms that remain long after the glacier has disappeared. 每一主要冰河期都产生特殊的地形，这种地形一直保留到冰川消失之后很久。He did not know any English before he went to England. 在去英国以前，他一点儿英语都不懂。After she finished her work, she hurried to the nursery to pick up her child. 干完工作后，她匆匆赶到托儿所接孩子。