OG2018对D的官方翻译：树里的水是他生长时的雨水（代表1600到2400年前的雨水），山洞里的水是更久以前沉积的雨水（代表比2400年前还要早的雨水）。所以没有可比性。
雨水里有D，用木头里的D含量推测降雨量。很久以前在北美的树里有很高的D，比现在的树含量高。但是同期洞穴里水的D物质含量去没有现在北美雨水里的含量高。 GAP：为什么同一时期树里的D比洞穴水里的D含量高 E：不是问那个时期木头和现在木头的D含量比较，gap不对。 D: 说明tree里的D才是当时雨水里的D，而洞穴水里的D不是同一时期同一来源的。

区分大猩猩和其他动物的是capacity for MSR 而不是 exhibits social behavior

1.句子结构，这是个强调句啊！要不是因为....，星星就可以...
后面一定要是个完整的句子，而且主句必须一开头就是主语，AB错
2.动词时态，CE的have肯定是错的。
3.句意推理，have caused a star's collapse，E的这个句意错了，是哪个星星的？不是他本身？E错

Command subjunctive
Bossy verb + That+subject+ bare form of verb：the infinitive（to be，to do）without the to

(D) "Charge X amount" is perfectly parallel to "charge Y amount" in the first half.

(E) "Those charging" has no counterpart in the first half.

一、时态。天体的远近是客观存在的，因此用现在时，所以that were 错了
二、so...that 结构。变成 so...for 明显错误

c 公立学校老师数量，现在比上一次recession之前多20%－陷阱是我们会想这些多出来的就是上次recession期间雇的呀，这里有两个错误：第一以史为鉴由过去推测将来是gmat的一个fallacy，第二现在下这个结论是政策有变化，刚刚才决定公立学校始终免费，老师学生比不变，所以上一次recession没这个限制，新政策和此前的老师增加没关系

C的错误在于后半句。第二句并不是质疑这个assumption，第二句质疑的是由这个assumption所推导出来的“many companies charge the greatest price the market will bear when they have such a product”这个结论。

竖着一列一列加就得了，很多数的加法运算，只要有正负数一定要结合正负使得数字变小。这个题7列，加到第四列就知道每一列的合都差4了。

B. Correct. Suppose that the flies that did not avoid the odor when tested individually were more likely to avoid the odor when in groups. This may be simply because these flies were following the movements of the flies that were triggered. That is, the signal did not cause the other flies' reactions. Instead, the movements of the triggered flies did. It follows that this possibility must be ruled out in order for the hypothesis to be plausible, and this answer choice does precisely that.
结论：在群体测验中飞走是因为收到了其他苍蝇释放的信号 削弱：不是因为收到信号，而是单纯跟着同伙一快飞

E receive support by sb用法错误，我们只能说receive support of sb/from sb
另外 DE的错误在于改变逻辑语义，因为DE用consistent修饰了support，而本来应该修饰receive的

C 整个结构不如E平行
Laos has a land area XXX but a population XXX
a land area that is about the same size as Great Britain's land area 这句话不对
you can say that two AREAS are the SAME.
you can also say that two pieces of LAND (or two COUNTRIES) have the same SIZE.
it's incorrect to say that two AREAS have the same SIZE.

E选项：adulthood身后少了逗号，插入语必须头尾用两个逗号将其隔开，例如：
James, a famous movie star, is friendly.
例句中，a famous movie star就是插入语，被两个逗号隔开。

AB: it is not clear what the modifying phrase depending on mass is supposed to modify. Because of its placement, it appears to modify red giant stage; it should, however, modify star. CE:the star itself passes through the red giant stage, not its mass.

前提：活动范围广的动物活得长
结论：活动范围广的动物种群数量会逐渐增多
gap：活得长的动物种群数量会逐渐增多

1/3....1 2^n是4的倍数

我在D和E之间纠结，最后选了E。有大神解释一下吗？