xy=1000

绳子没说一定是按整数减的

until recently
up to recently

另外，请注意，连词in that（in that和because意思相近，都是因为的意思）是没有错误的，在GMAT的官方考题的正确选项中出现过，因此万万不可因为不熟悉in that而排除本选项。

插入语是插在句子中的一个词/短语或句子，用两个逗号隔开，与句子的其他成分没有语法关系，可以视为独立成分。通常是对一句话进行解释、补充。
A中的having amassed，因为有逻辑主语，所以既可以看成是伴随状语也可以看成是插入语，都是在修饰 Neuroscientists are drawing conclusion这个句子。伴随着积累知识，他们形成了结论。

D/E，按图形背景原理形成结论发生时间短于经过20年的积累知识，前者做主句更优。

现在分词做伴随状语起到伴随的动作和伴随的结果两种功能，如A就是伴随着积累知识的动作，形成了结论；E是他们积累知识，伴随的结果是形成了结论。
伴随的动作表示与主句动作同时发生，having则表示先时性；伴随的结果需要是主句动作的直接的、自然而然的结果。E积累知识并不会自然而然就形成结论，drawing conclusion用法不好。

段子的结论是社交可以帮助老人保持思维敏锐
--要削弱evidence，就可以削弱这个study不具有代表性，不是对所有人适用，是biased的。
C选项正确，因为治病导致思维敏锐度下降的同时也会导致社交自闭。
对于这一个群体来说，社交不能够帮助他们保持思维的敏锐，所以社交这个方法存在counter example，对某一些人不适用（对应“ sufficient”），削弱。

https://www.manhattanprep.com/gmat/forums/nine-months-after-the-county-gprep-sc-t4953.html

the same reasoning applies here; you're looking for idiomatic usage that agrees with 'risk', not 'chance'.
the last poster is correct in one sense, which is that there are correct idiomatic usages of 'chance to'.

as small a collection as three pirated albums has occasionally drawn the attention of the recording industry.
in this case, 'collection', not 'albums', is the subject of 'has drawn' (which can be inferred from the fact that 'has' is singular).
this is the case because this sentence is equivalent to the following rearranged version:
a collection as small as three pirated albums has occasionally drawn the attention of the recording industry.

带伴随状语的，主句主语最好是直接放在主句句首，使伴随状语的逻辑主语一目了然。

it 指代的是rise，C因此没有指代对象，reach its highest level 是结果，所以用ing形式

In #C there's no NOUN that serves as the focus of the modifier 'resulting from...' (an adjective-type modifier). It's intended to modify the general idea that the orbits have become littered, but there's no NOUN that signifies the littering.

#D has the same problem as #A ('because' is wrong).

Choice A doesn't convey the right meaning. If I say that littering occurred 'because of' the intentional discarding of those items, that implies that the intentional discarding WASN'T the actual littering. Instead, it means that the intentional discarding set into motion a chain of events that LED to the littering.

so/that与because/(so):
So many people removed, that the population declined. VS Because many people removed, the population decline.
so/many，because(so)都有因果的意思，差别在于so/many直接强调了多，因为如此多的人搬离，所以人口下降；because则表示是因为很多人搬离这整件事导致人口下降。

C中as early as the eighteenth century作为状语，表示（早在18世纪时）leaching是方法，而D中that was as early as the eighteenth century是定语修饰method，表示leaching是（18世纪的）方法。我们一般说，早在某个时候，某物就已经是……

do指代的是know，如果不加they do，变成have to know a great deal more than they have to now，语意应该是“比现在知道的要多”，而不是“比现在不得不知道的要多”，所以they do不能省略。
would可以表示意愿及可能。

https://www.manhattanprep.com/gmat/forums/sc-several-financial-officers-of-the-company-spoke-t13620.html

A. It is reasonable to infer from the given information that some aspect of the computer model is incorrect in some way. One way that it might be incorrect is that the measurements of atmospheric levels of carbon dioxide used are inaccurate. Nevertheless, there is not sufficient information to infer that this is the specific flaw in the model.

If the model were correct, its predictions would be confirmed by the data regarding warming. However, this has not occurred. It is therefore reasonable to infer that, in some way, the computer model is incorrect.

https://www.manhattanprep.com/gmat/forums/for-protection-from-the-sun-the-mojave-t8912.html