摘要： 现在完成时 1) 用法: A) 表示动作到现在为止已经完成或刚刚完成. 例:I bought a new house, but I my old one yet, so at the moment I have two houses. A) didn't sell B) sold C) haven't sold D) would sell 答案是C) haven't sold. B) 表示从过去某时刻开始.持续到现在的动作或情况.并且有可能会继续延续下去.此时经常用延续性动词.时间状语常用since加一个过去的时间点.或for加一段时间.或by加一个现在时间. 例:Great as Newton was, many of his ideas today and are being modified by the work of scientists of our time. A) are to challenge C) have been challenged B) may be challenged D) are challenging 全句的意思是:“虽然牛顿是个伟大的人物.但他的许多见解直到今天还在受到挑战.并且被现代科学家的工作所修正. challenge是及物动词.在本句中应当是被动语态,其动作延续到今天.所以要用现在完成时态.可见答案是C) have been challenged.A) are to challenge和D) are challenging都是主动语态.不可能是答案.B) may be challenged虽然是被动语态.但意思与全句内容不合.所以不对. C) 表示发生在过去.但对现在仍有影响的动作或情况.通常用点动词.如:arrive, begin, find, give, lose等. 例:John has broken his left leg. 2) 注意事项 A) 现在完成时是联系过去和现在的纽带.现在完成时和过去时的区别在于:现在完成时强调动作的动态.或受动态的影响.是动态的结果.对现在有影响,过去时只表示过去的某个具体时间里发生的动作.与现在没有联系. 例:He worked in that hospital for 8 years. 他曾经在那家医院工作了8年.这只是讲述一个过去的事实.他现在已经不在那家医院了.) He has worked in that hospital for 8 years. 他已经在那家医院里工作了8年.表示他从过去开始工作.一直工作到现在.现在仍在那家医院工作. B) 因为含有for加一段时间或since加一个时间点这样的时间状语的完成时.有动态和延续性的特点.所以不能使用终端动词或瞬间动词. 例:My sister has been married for 5 years.(过去分词做表语表示状态.可以延续) My sister has married. Don't disturb her. C) 在"this is the first/ second/ third-- time that--"句型里要求用完成时. 例:This is the second time that the products of our company have been shown in the International Exhibition.(这是我公司产品第二次参加国际展览会.) D) 句型"It is/ has been--since"所使用的两种时态都正确. 例:It is/ has been 10 years since I last saw him.(从我上次见到他以来已经10年了.) E) 在"no sooner than"."hardly/ scarcely --when"."before"."prior to"等句型中.主句要求完成时. 例:I haven't met that professor prior to today.(以前我从未见过那位教授.)

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