B选项之所以不能选，我觉得应该是因为：只是有部分的fullerence来自陨石，但是不影响科学家拿其他的提到的矿中的fullerence去测算啊

E选项把带回从句说不通，collect的不是severance package！

根据Ron：based on, due to, caused by只可修饰noun（如主语），不可修饰句子！
但是because of 可以修饰句子，according to应该也可以

宾语从句是最关键的问题；
而且这儿还不可以用based on！！1) Based on XXX, Subject + Verb. (修饰Subject). 修饰后面的主语

also:
in general, OBJECTS OF PREPOSITIONS are very rarely the antecedents of pronouns. (i won't say never -- but rarely enough that, if you have to make a random guess, this is probably a pretty good standard by which to make such a guess.)

HOWEVER,
2) if you see an ambiguous pronoun that is NOT replaced by the correct noun in any of the other answer choices, then DON'T eliminate!
for an example, see problem 21 in the blue verbal supplement (in which the correct answer contains a technically ambiguous pronoun).
or see the problem in this thread!

1) if you see an AMBIGUOUS PRONOUN that is REPLACED BY THE CORRECT NOUN in OTHER ANSWER CHOICES, then ELIMINATE the ambiguous pronoun and keep the specific noun.
for an example, see problem 68 in the blue verbal supplement, in which "them" is split against "these companies".

Ron:
C选项：(c) suggests that even natural growth still has to be performed by the suppliers.

D选项是否存在代词不明确的问题：
this is a good point -- the correct answer to this problem, yet again, contains a pronoun that is technically ambiguous.

however, as we've seen again and again and again and again, not all ambiguous pronouns are incorrect!

so here's the simplest way of making the decision:

因为是整数且p不可被m整除，所以问r是否>1其实反过来就是问r是否=1，也即是否p=mk+1恒成立（k为整数）。
选项1把p=2x, m=2y代入即可；选项2好像是能笨办法试了，还更快一点

审题，选项2只说了shipping fee，没说processing fee。。

此题不需要两个选项就能恒成立，这也是正向推导的结果；不过做题的时候为快捷，还是从选项出发逆向验证比较快。

犯罪率和犯罪增长率的比较。 假如M地区四年前的犯罪率是10%，现在增长了40%也不过是50%的犯罪率，但是P地区四年前的犯罪率是80%，现在增长了10%就达到了90%的犯罪率了，按照这样来说很可能还是P地区的犯罪率高，人民更容易受害，所以知道四年前的犯罪率很重要。这样理解是对的不

C选项population用了复数不算错误么？

clones代表克隆的个体，克隆的个体们，和cheetah species的个体们做比较。由unlike引导的名词间的比较。个体和个体做对比，如D，而不能个体和一个种族（指整体）做对比，如错误选项B

It is known" can't apply to past dates

总尾气=idling+driving 修停车场只能减少idling的尾气

因为 Before the time 不谢

老师，问题问题如下：
A、they能否指代recent studies，即研究认为......
B、按照比较，不是应该加助动词do livestock，才能和左边平行么？比较的对象是less fat，所以应该用wild animals have和do livestock，为什么没有do也对呢？

(x-y)^2 = x^2-2xy+y^2

Proved通常用主动表被动