三、完成时
完成时包括现在完成时、过去完成时、将来完成时、过去将来完成时。
1.现在完成时表示到现在为止所发生的动作或状态;也表示对现在有影响的已经发生了的动作:
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 B)may be challenged
C)have been challenged D)are challenging
牛顿虽然伟大,但他的许多思想今天正受到我们时代的科学家的挑战和修改。（B4，1997.1-40， C对）
My watch has stopped， so I cannot tell you the time. 我的表停了,所以没法告诉你时间。
注意现在完成时常与yet， already， recently， just， never, ever等状语连用;而过去时与just now 连用:
Whatever the causes， English at the end of the 20th century is more widely spoken and written than any other language .
A） ever was B） had ever been
C） has ever been D） would ever be
（B6， 1995.6-43，C对） 无论由于什么原因,到20世纪末,不论是口头语还是书面语,英语比迄今为止以往任何语言都用得广泛。(ever表示“迄今为止任何时候”at any time up to now)
This is one of the most exciting film I have ever seen.这是我所看过的电影中最激动人心的一部。
She told me about that just now.她刚才告诉我那件事。
since 从句用一般过去时,主句用现在完成时,这种句式很常见:
You haven't changed much since we last met. 自从上次分手后你没有多大改变。
It's been over a year since I came back from the countryside.我从农村回来已经一年多了。
当主句的动词为be或seem，表语为表时间的词语时,主句用一般现在时也很常见,因此,上句也可改为:
It's over a year since I came back from the countryside.
2.过去完成时表示过去某时之前已经发生的动作或状态,常与by the end of last year， up till then 之类的时间状语连用;或表示某一动作较另一过去动作之前发生。例:
Until then， his family from him for six months.
A） didn't hear B） hasn't been hearing
C） hasn't heard D） hadn't heard
到那时候为止,他的家人已经六个月没有收到他的来信了。(B4， 1997.1-21，D对)
Mrs. Lackey was awakened by the ringing of the bedside phone 12 hours after her husband's boat had been wrecked. 拉基女士床边的电话响了,把她从睡梦中惊醒,那是在她丈夫的船失事后12小时。
3.将来完成时表示将来某时会业已发生的事情,常与by the end of next month， by this time next year之类的时间状语连用;也用来表示一种揣测:
By the end of this month， we surely a satisfactory solution to the problem.
A） have found B） will be finding
C） will have found D） are finding
到本月底,我们肯定能够找到一个满意的解决问题的办法。（B4，1993.6-45，C对）
I have been studying here for four years， by next summer I shall have graduated. 我在这里学习已经四年了,到明年夏天我就毕业了。
4.过去将来完成时
这个时态表示从过去某时看将来某时会业已完成的动作:
I hoped my wife would have got everything ready before the guests arrived. 我希望我的妻子在客人到来之前把一切都准备好。
5.表示延续动作的动词如run， study， stay等用于完成时,常与for短语、since短语或since从句连用,表示动作延续一段时间;另外一些动词如die， open， go， come， join， leave， begin， end, arrive， cut 等表示瞬间动作的动词用于完成时,就不能与这些时间状语连用。
“他离开这个城市已经三年了”不能说成“He has left this city for three years.”;应该说:“He left this city three years ago.” 或“It is three years since he left this city.”
