its是代词，其指代对象在本选项中是没有问题的，是crust? 这个说法不对吧。A的主语不是earth么？

选对了，但是选项D的情况应该在什么时候使用

Ron I'm pretty sure that either "when" or "at which" would be acceptable. i think (not 100% sure) that "the date when" is used for actual, precise calendar dates, whereas "the date at which" is used for the usually more vague dates of historical events, such as the one in this problem. But i'm sure the test is not going to depend on this sort of nuanced difference.

be known to have done sth的问题：当be known 和 do sth的发生的时间一致时，用be known to do sth；而do sth发生在be known之前时，则要用be known to have done sth。 这个解释我觉得好理解点，约束力这种概念太模糊了

Since 1987, Santer argues, the greenhouse effect has reasserted itself, and the north has taken the lead.

选项A amounting错误修饰One automobile manufacturer，同理排除AB

读原文的时候又囫囵吞枣
看选项定位原文的时候对于一些[类似]的词没有重视：[influence] [importance] 看起来都是很正面很大的词语，但是意思完全不一样，要注意。

3和6都有可能

先算税再subtract

选项a 第一个逗号前面有一个and

(A) 正确，由and连接的两个并列的强调句，注意此处两个并列结构中的it不是形式主语，而是强调结构中的it。

(B) Katharine Graham’s becoming不简洁;and连接的两个句子不平行

(C) 代词that只能指代名词，不能指代整个句子;having won high praise under her command修饰KG这个人错误

(D) 句子缺谓语

(E) Katharine Graham’s becoming的表达不简洁；句子重心变化

of A and of B - A的混合物和B的混合物
of A and B- A+B的混合物

such effects could lead to several precursory phenomena in the field, including a change in the velocity of seismic waves, and an increase in small, nearby tremors.

record-breaking 看选项的时候要仔细，力求把每一个选项都看懂，不要囫囵吞枣

by these countries' standards。。。感觉很隐晦

adjective] ENOUGH to..." means, basically, "sufficient to meet a threshold/minimum requirement".
"SO [adjective] that...", on the other hand, is used to emphasize that something is EXTREME.
again, just make up examples in your head -- this time using "so big..." or "so tall..." or "so old..."
if your examples make sense, then, ALL of them will emphasize the EXTREME quality of whatever you are talking about.

adjective] ENOUGH to..." means, basically, "sufficient to meet a threshold/minimum requirement".
just think about typical examples of being "tall enough" or "old enough" or "good enough" for various things. these are NOT examples of "extremes"; they're just examples of "things that meet minimum requirements".

第二遍错了……语义！！！

考察Allow的用法

Allow to do, allow..to do, allow that(不加虚拟）

AD语义不对，allow that表示 同意，承认，不表示允许

B and so没有平行对象

C 允许某人做某事，直接用allow ...to do而不用allow for...to do

E 正确，而且so that 表示结果

D的选项应该是这样的吧？
Leakey's contributions to archaeology include her discovery of the earliest direct evidence of hominid activity and her painstaking documentation of