mark,
A is to B what C is to D是一个习惯表达

a错是因为work是动词，which修饰人是不允许的
e as in much of Eastern Europe, an overwhelming proportion of women work, many of them in，，，many of them作为同位语。。

还原倒装： Halley's comet caused such a worldwide sensation in no other historical sighting as in its returning of 1910-1911

capable of doing
capability to do
ability/ability to do

double在这里是动词啊，也可以被more than 修饰：
that personal spending in the July-September quarter would more than double the 1.4 percent growth rate in personal spending for the previous quarter.
e中that of没有核心词，多余

three times the price that。。。倍数直接加对象

用their时看有无明显指代，如果没有则错

长句子注意找有没有有效动词

because of后面只能加名次，代名词

e，见到both，想平行

so 。。that。。。so离得很远

D选项：the Sun has the same apparent size in the sky as the Moon's.
是对的。
参考GMAT SC里的一个正确句子（有简化）：
Wild animals have less total fat than that of livestock fed on grain.
只要比较的对象合理，且不会引起歧义，就是合理的。

虚拟语气 were，看到were就排除了没有多想想

C选项：首先，过去完成时表示这个事件发生在过去的过去，但本题没有明确表示这个事件发生在哪个过去时间的过去；其次，并列连词and引起的关系错误同选项(A)。

想哭，GMAC就像一个步履蹒跚的老头，走起来特别慢，只能从A到B，不能从A到C，更别提到G！
A选项 VS B选项
三件事情：A-生物在经受食物短缺；B-食物短缺了；C-海面温度上升，逻辑：因为海面温度上升，所以食物短缺，因为食物短缺，所以食物在经历这个短缺。
A选项：a result from increasing是独立主格，修饰主句生物在经受食物短缺，C-A，错！
B选项：food supplies were dwindling as a result of an increase in temperature，C-B，对！

a中， the company 单数，后面their，单复数没考虑充分

平行， by
。。的数量“的说法：
their numbers are。。。。的数量。。
the number of them is

D
比较中省略的原则在于是否会造成歧义。如果省略能使比较更清晰就省略；如果省略会带来比较上的歧义，则不能省略。省略的一定不是比较的重点，省略是为了更好地突出比较的重点。
D，rats was fed a diet that has at least 30 percent fewer calories than they would normally eat
这里被比较部分省略了定语或比较的主体diet，than (the diet) they would normally eat，但不会引起歧义。
另一个例子：Rice has protein of higher quality than that in wheat.
That不能省略，因为比较的是 protein in rice VS protein in wheat,不是rice VS wheat

B的with是修饰主句 是状语，修饰动作，一般带with的迷惑选项都是不对的，无法区分时，尽量选从句修饰

if choice a actually has the original wording posted at the beginning of this thread ('will it' instead of 'it will'), then it's definitely wrong. 'will it' is only ok in the context of a question ('will it rain tomorrow?'), and can't be used as a noun phrase.