ChaseDream

标题: 关于时态的问题，GWD17-Q32 [打印本页]

作者: wzl36 时间: 2011-1-27 14:30
标题: 关于时态的问题，GWD17-Q32
Navigators have known for thousands of years that the ocean has variable currents, but it is only in the last half century that a reasonably clear picture has emerged of the patterns and causes of ocean currents.

A) a reasonably clear picture has emerged of the patterns and causes of ocean currents
B) a reasonably clear picture of the patterns of ocean currents and their causes have emerged
C) a reasonably clear picture emerged of ocean currents, their patterns and the causes of them
D) there have emerged a reasonably clear picture of the patterns of ocean currents and what caused them
E) there had emerged a reasonably clear picture of the patterns of ocean currents and their causes

答案是A，我的疑问是既然发生在“ in the last half century”，为什么要用完成时，不用过去时？

作者: evelyn205205 时间: 2011-1-27 15:11
in the last century, lz要记住哦，是大段时间，要用现在完成时
用现在完成时的标志：
1. since
2. 大段时间如in the pat several years, in the last century, in a period of time
3. 出现has ever seen或者than ever before possible等字眼

作者: wzl36 时间: 2011-1-27 16:19
啊，终于明白了，谢谢，所以下面这句也是这个原因才用完成时的吗？

All Y chromosomes in existence today are descended from a single ancestor’s who is thought to have lived about 140,000 years ago.
A) a single ancestor’s who is thought to have lived
B) a single ancestor’s who was thought to live
C) a single ancestor whom it is thought had lived
D) the Y chromosome of a single ancestor who is thought to have lived
E) the Y chromosome of a single ancestor whom it was thought had lived

作者: li2966262 时间: 2011-1-27 21:07
但是不懂的是 but it is only last half century 里面为什么用IS而不用WAS呢？

作者: wzl36 时间: 2011-1-27 22:03
这个我知道，因为是强调句 it is ... that... 还原就是
in the last half century，a reasonably clear picture has emerged of the patterns and causes of ocean current

作者: aeoluseros 时间: 2011-1-27 22:17
in last century和in the last century有区别。
in the last century是指到这一瞬间截止，往前倒数的一个世纪，即1911年1月27到2011年1月27.（当然对于大范围时间不必如此精确）
而就我们这个时间2011年1月27号来言，in last century就是指20世纪了.

作者: aeoluseros 时间: 2011-1-27 22:18

啊，终于明白了，谢谢，所以下面这句也是这个原因才用完成时的吗？

All Y chromosomes in existence today are descended from a single ancestor’s who is thought to have lived about 140,000 years ago.
A) a single ancestor’s who is thought to have lived
B) a single ancestor’s who was thought to live
C) a single ancestor whom it is thought had lived
D) the Y chromosome of a single ancestor who is thought to have lived
E) the Y chromosome of a single ancestor whom it was thought had lived

-- by 会员 wzl36 (2011/1/27 16:19:30)

is thought to have done中have done其实是表示往前推一个时态，来区分is thought to do，因为to后面一定要跟动词原型，所以要做如此区分，所以，have done并不是表示完成时。

作者: wzl36 时间: 2011-1-27 22:21
可不可以理解为in last century 用过去时in the last century用完成时？

作者: sunshengkun666 时间: 2011-7-14 16:33
班主能不能解释下A项，我怎么觉得of the patterns and causes of ocean currents 跟在emerged后面这么别扭呢~~求解释~

作者: nemiah 时间: 2011-7-14 16:41

-- by 会员 wzl36 (2011/1/27 16:19:30)

-- by 会员 aeoluseros (2011/1/27 22:18:54)

版主牛人！

作者: 小熙 时间: 2016-6-19 17:24
感谢分享！

欢迎光临 ChaseDream (https://forum.chasedream.com/)