Answer choice A puts the events in proper perspective:
* The comet disintegrated last year; this was a one-time event.
* It provided new insights. Since it was a one-time event, it's appropriate to say 'provided' (simple past tense), unless the same event has CONTINUOUSLY provided newer and newer insights, in which case 'has provided new insights' would be better. But there's no indication of the latter in this sentence.
* The 'forcing' is a possible future event.

According to choice E:
* The comet's disintegration produced new insights last year.
And, more absurdly,
* The disintegration produced those insights in full view of ground- and space-based telescopes!

from this example, you can learn that 'as well as' is not strictly a parallel marker.incidentally, in the official correct sentences, i've never seen 'as well as' followed by anything other than a noun. (remember that '__ing' can be a noun; that's the role played by 'emitting' here.)

i wouldn't elevate this to the status of a 'rule', since as well as is also widely used to connect other things, such as adjectives (His review was insightful as well as thorough).

on the other hand, i am comfortable positing these two things:
• don't follow 'as well as' with a verb
• be suspicious of any choice in which 'as well as' is followed by something other than a noun. (if you can't see any other reason to eliminate, use this as a guessing method.)

BCE与原文信息直接相反；
D 中雨的降雨总量（注意是全年总量！不是单次的），1990是1910的两倍。假设，1990的单次降雨都是2 inches，1910的单次降雨都是1 inches，只有在1990的中雨天数 大于或等于 1910的中雨天数时成立。然而1990的降中雨天数一定是小于1910的，所以一定不成立。
A：次数少，但是每场都是大暴雨

i do believe that we've seen examples in which relative pronouns stand for the entire phrase 'X of Y' rather than just the Y immediately preceding the comma, but that situation is rare indeed and should be avoided unless absolutely necessary (= it happens in all the choices, so you can't get away from it).

in this case, then, choice e, which avoids this whole relative-pronoun mess, is certainly preferable to choice d, which doesn't.

still, you can rule out choice d for other reasons:
* 'seemed to be using': unacceptable change of meaning. the past-tense 'seemed' says that that's the way it seemed to the mayans living in cancun long ago, whereas the sentence is clearly designed to say that's the way it seems to us now.
* i don't like 'in becoming', which smacks of what the gmat would call 'idiom error'. there's no answer key for these things, of course, but i do have the feeling that the gmat would label this as an idiom error.

Though it is not a definitive grammatical principle, sentences with infinitive forms are often less awkward and wordy than those with the -ing (progressive forms). In this particular case, not only is "looking at" in choice E nonsensical, as to look at implies visual skills rather than logical considerations, but also the verbs using and attract are not parallel. Answer choice C, the credited response, correctly employs the parallel verbs improve and attract.

well, strictly speaking, a waterfront is not a way of doing something; it's a physical frontage that is just sitting there next to the water. So, literally, that statement is nonsense.
More importantly, if you compare that choice against choice (C), you should notice that (C) is more concise and better worded.
(That's the way you should make all decisions about "wordiness""”they should be relative decisions, not absolute decisions.)

well, d has two problems, at least:
- 'projects X to do Y' is unidiomatic. (you can just say 'projects NOUN', as is done in choice e, or you can say something like 'projects that X will do Y').
- an average is a single data point, so there's no such thing as 'averag[ing] from 1.8 to 6.3'. on the other hand, it's quite possible for a single data point to fall between two given values.

i've seen 'of between' in this sense before - think of the phrase 'between 1.8 and 6.3' as standing for a single number, and parse the sentence accordingly (it reads as if it said 'average g.w. of 5 degrees', for instance) - so, if the original poster has copied the problem correctly, we now know that the gmat accepts that construction.

Prep2007E1-SC-154

In general,

1 * if you have than/as + subject + FORM OF "TO BE" as the second half of a comparison, then you must have another form of "to be" in the first half of the comparison.
or, there should be something in the first half that would make sense with "to be" in front of it.

2 * if you have than/as + subject + HELPING VERB as the second half of a comparison, you can have just about any other form of the same verb in the first part, as determined by context.

3 * if you have than/as + subject + FORM OF "TO DO" as the second half of a comparison, then you must have an ACTION VERB[/b] (or another form of "to do") in the first half of the comparison.

here are some examples:
#1
the air quality of las vegas is higher this year than it was in 2005.
parking spots are disappearing much more quickly today than they were yesterday.
#2
james can negotiate with salespeople more effectively than stephanie can. (comparing their abilities)
james can negotiate with salespeople more effectively than he does. (his ability exceeds his actual performance, probably because he just isn't trying very hard)
#3
parking spots disappeared much faster today than they did yesterday.
tanya eats more slowly than she did when she was a teenager. (note that "did" doesn't have to have the same tense as the action verb)

B) you can't use 'that' in this sort of construction, because constructions using 'that of' (or other preposition after 'that') must have EXACTLY parallel structures. in other words, if the second half says 'that during 10,000 years', then the preceding half must say 'the growth of ___ during something else' (or some other time preposition, such as before or after, in place of during).

there's nothing ungrammatical about 'from when', because the clause starting with 'when' is a perfectly legitimate noun clause (i.e., 'when agriculture began' serves as a noun. however:
- regardless of where the gmat stands on the issue, 'the beginning of agriculture' is unquestionably better than 'when agriculture began' (i.e., an actual noun is almost always superior to a circuitous noun clause, when possible)

C) first, you've got a "which" modifier that isn't preceded by a comma, so that's an automatic failure. (note that you can use preposition + which without a comma -- e.g., the box in which you placed your valuables -- but you cannot do so with just plain "which".)
more importantly, "had been" is not parallel to anything in the other half of the sentence; in order to use a parallel structure that contains a form of "to be", you must have another form of "to be" in the other half of the parallel structure.

D) you can't use the present perfect if the time interval is over. If the trend continues into the present day, then the present perfect is appropriate.
Even if that were fixed, choice D still suffers from fatal wordiness / lack of concision, especially in comparison to the correct choice."

E) 'what it did' doesn't make any sense:
* the growth didn't 'do' anything
* there's no other verb to which 'did' could logically be parallel to complete the comparison

比较前后状态一致

把主谓抽出来jay can remember and tends to

the fused clavicles (the "wishbone") of birds differ from the unfused clavicles of theropods.-->鸟类的锁骨是fused而theropod的是unfused（这是两种不同样的骨头），所以认为鸟类不是从theropod进化来的
B中的内容是作者提出的，科学家对于lung这一点只是提出质疑lung并没有说evidence的事情

第一过完必须要谨慎，第二突然出现的代词要找到先行词

第三題: Ad revenue (in $) per dollar charged for advertising impressions
CPM=1(per dollar charged)=Ad Revenue / (Readership * Pages)
因此Ad Revenue=Readership * Pages，找Readership*Pages最大(即revenue最大)

B are subjected to; as + n 作为的语义
C as错

注意题中有提示being China's first administrators；their empire所以要用复数

在逻辑上，限制传播的是复数名词fierce intercolony struggles，而不是单数名词kind。 kind是种类的意思，种类不会限制传播。

A 试图通过一个变化对当前成员的影响 来推断对潜在成员的影响。当前的菜鸡们没能力做讲座，不代表最优秀的候选人不做讲座。
E 假定对大部分成员有益的变化将对所有成员都有益。P并没有对有益的涨工资部分进行反驳，而是对有害的禁令进行了反驳，所以不对。

在动物园会感染的员工会转业，那么留下来的都是不太容易感染的了，不容易被感染的人的可能有30%，那么动物园外的普通人感染概率就高了