it/they同物指代，that/those异物指代
这个句子可以改写成：
more than ten times as much energy is generated through wind power now as in 1990 或 as that in 1990 或 as was the case in 1990

so/such/case可以指代句子/一件事情，如：
No one do so, even though there are more apples in the trees can be picked this year.
The sun ejects red fire, as is the case with any star of similar mass.
Cells secreted hormones, in which case they were endocrine cells.

it指代对象是more than ten times as much energy, 因此在选项中出现的代词it都是不合理的

there are two splits you should use to narrow down this problem:

(1) the second half of the construction 'ten times as much ... ____' is as, not than. therefore, you can eliminate answers (a) and (e), which contain 'than'. (i'm assuming that (e) is supposed to say 'than', not 'then'; i don't think the gmat problems would that blatant an error)

(2) the pronoun 'it' is inappropriate, because 'it' must refer to the ENTIRETY of the noun phrase serving as an antecedent.
for instance, the following is an improper sentence: last year's attendance was ten thousand greater than it was this year
in the above sentence, the pronoun 'it' must necessarily refer to last year's attendance, not just attendance.
the problem in this post has the same issue: the pronoun 'it' must refer to more than ten times as much energy, not just energy - an interpretation that makes no logical sense. therefore, all answer choices containing the pronoun 'it' are wrong.

if you don't like '...than was the case', you should learn to like it; this is one of those phrases that the gmat writers use to refer to concepts that don't fit under the usage constraints of traditional pronouns. (another popular one of these constructions is 'do so'.)

忘了忘了，it是同物指代，要用that，这里只能用the case

R：the air quality of las vegas in 2007 was higher than that in 1997
W: the air quality of las vegas was higher in 2007 than that in 1997，前面部分的名词和in 2007之间被谓语动词隔开了，后面that in 1997却没有这样一个动词
R：the air quality of las vegas was higher in 2007 than in 1997，it指代the air quality of las Vegas，两部分时态一致，动词可以省略
R：the air quality of las vegas was higher in 2007 than it was in 1997

if you don't like '...than was the case', you should learn to like it; this is one of those phrases that the gmat writers use to refer to concepts that don't fit under the usage constraints of traditional pronouns. (another popular one of these constructions is 'do so'.)

1. it属于准确指代，即it指代的energy就是前句说的more than ten times as much energy，然而这里指的是两个不同的energy，而不是同一个energy，所以要用was the case来代替。it的前置词是无意义的，所有使用it的都是错误的选项。
2.只能用the case概括，C选项是一个倒装：the case was in 1990
3.as……as结构

对比句前后，it一定是同物指代（前后都是同一年风力产生的电能）
做对比局的时候，把as/than前后的成分单独拆开看，C选项是一个倒装：the case was in 1990

it是关系代词，而每个代词在句子都需要明确的所指代的对象即前置词。从整个句子看，冒号后是个独立完整的句子，句子的主语是more than ten times as much energy，且是该句子唯一的名词，故而it指代的是more than ten times as much energy，注意不是energy。而此处more than ten times as much enery在此处作为it的前置词是无意义的。所以所有使用it的都是错误的选项。
只能用the case概括

it指代？

it指代不明，不可乱用

it的指代的问题，ron说it指代的是 more than ten times as much energy。

先由as...as结构排除AE，然后根据语义 it属于准确指代，即it指代的energy就是前文说的more than ten times as much energy，然而这里指的是两个不同的energy而不是同一个energy所以要用was the case来代替，指代in 1990的情况

1. 考察的是as ... as 结构，由此排除 A/E；
2. it是关系代词，而每个代词在句子都需要明确的所指代的对象即前置词。从整个句子看，冒号后是个独立完整的句子，句子的主语是more than ten times as much energy，且是该句子唯一的名词，故而it指代的是more than ten times as much energy，注意不是energy。而此处more than ten times as much enery在此处作为it的前置词是无意义的。所以所有使用it的都是错误的选项。

"as was the case" isn't a pronoun, so it doesn't refer just to a single noun. It can refer to an entire clause.

对比的是现在收集能源和以前收集能源，则the case in 1990是正确的对比

if you don't like '...than was the case', you should learn to like it; this is one of those phrases that the gmat writers use to refer to concepts that don't fit under the usage constraints of traditional pronouns. (another popular one of these constructions is 'do so'.)

in the above sentence, the pronoun 'it' must necessarily refer to last year's attendance, not just attendance.
the problem in this post has the same issue: the pronoun 'it' must refer to more than ten times as much energy, not just energy - an interpretation that makes no logical sense. therefore, all answer choices containing the pronoun 'it' are wrong.

以下解释可能会有所帮助：
the pronoun 'it' is inappropriate, because 'it' must refer to the ENTIRETY of the noun phrase serving as an antecedent.
for instance, the following is an improper sentence: last year's attendance was ten thousand greater than it was this year

as be the case+prep这个结构到底怎么用，我看有不少题目都有这个结构，一个网络药店的题，还有个什么题目我忘了
貌似是prep后面的这个事情和主句的事情不需要严格平行。希望毕老师能够回答一下，谢谢！