天山-7-41

zuozuox

但是C的完成时态真的是个问题，为什么用完成是呢？

ladun

re! at the date human have done sth时态不匹配。C不对

mhe2

以下是引用songlovegt在2009/4/13 21:04:00的发言：

Scientists
have dated sharp-edged flakes of stone found in the fine-grained
sediments of a dry riverbed in the Afar region of Ethiopia to between
2.52 and 2.60 million years ago, pushing back by more than 150,000
years the earliest date when it is known that humans made stone tools.

1. when it is known that humans made
2. at which it is known that humans had made
3. at which humans are known to have made
4. that humans are known to be making
5. of humans who were known to make

又想到一点 when 修饰一段时间，at which 修饰一个时间点

260,000 - 252,000 = 8000 years

pushing back by more than 150,000
years

8000 years 相对于 150，000 years 只是一个零头，所以 the earliest date 的时间波动可以忽略，可以看成是一个时间点。at which 比 when 修饰准确。

另外状语从句不是必须修饰主句，应该也可以修饰分词，不定式
找到一个例子
GWD-29-Q10
The principal feature of the redesigned checks is a
series of printed instructions that the company hopes will help
merchants confirm a check’s authenticity, which includes reminders to watch the endorsement, compare signatures, and view the watermark while holding the check to the light.
A.        which includes reminders to watch the endorsement, compare signatures, and view
B.        which include reminders for watching the endorsement, to compare signatures and view
C.        by including reminders for watching the endorsement, comparing signatures, and viewing
D.        including reminders to watch the endorsement, comparing signatures and viewing
E.        including reminders to watch the endorsement, compare signatures, and view

while 引导的状语从句是和不定式to watch the watermark并列的

including reminders (to merchant) to watch the endorsement, compare
signatures, and view the watermark while holding the check to the light
这样的省略不常见，while不是必须和主句并列，而且逻辑上的主语可以都省

同学，2.6 million应该= 2，600，000吧？

换句话说，2,600,000-2,520,000=80,000

而且我觉得150,000不是和 (2,600,000-2,520,000)之差比较。应该是本来有个时间，但这个时间比2.52mil-2.6mil年前晚

sprins

anyname

buffonjuventus

anyname

-- by 会员 sprins (2009/9/3 20:15:00)

他的解释确实不错，而且我也的确觉得回帖比看OG更重要，攒RP啊……

游园惊梦似归客

anyname 发表于 2005-3-23 13:41
本来选A，仔细考虑后改支持C。做题时看不惯at which，稍微查了一下，the date when....和the date at which ...

同意！               

Sara.Z

zuozuox 发表于 2009-8-1 19:12
但是C的完成时态真的是个问题，为什么用完成是呢？

根据句意说的是最早的人类已经做出了stone tools，所以后面应该是完成时直接排除A,D,E.
B，is 后面跟过去完成时错，而且很wordy所以选择C。

kluivert

我抄袭来的，大家看看


The funny thing here is that (A) is more or less grammatically correct, but illogical. This is what is so tricky about GMAT SC --- it's not enough to be analyzing at the level of grammar. We have to take logic into account.

What the sentence is trying to say ----- (a) humans made tools 2.6 Mya, and (b) right now, we know this to be the case. There are two actions, happening at different times --- the tool making (2.6 Mya) and the knowing about the tool-making (right now).

Look at thhe grammatical structure in (A).
.... the earliest date when it is known that humans made stone tools.
What precisely is happening at that "when"-time? Is it the knowing or the making? Technically, the clause that immediately follows "when" is "it is known", so grammatically, this would suggest the knowing happened at this "when"-time, 2.6 Mya. But logically, we know that's not the case --- it's not the "knowing" that happened 2.6 Mya, but rather the tool-making. The knowing is what the paleoanthropologists are doing right now.

That's why (A) is wrong and (C) is right.

Consider these two sentences:
(1) It is known that early humans used stone tools.
(2) Early humans are know to have used stone tools.
Both are grammatically correct, but the GMAT would consider the second one more direct, more powerful, and therefore a much better answer than the first.