A 两个were之间没有连词
B with more than 75 carefully engineered structures 状语修饰were built, 意思是settlements 被建是带着75个建筑，of up to 600 rooms each 插入语修饰structures, 意思是每个建筑多达600个房间，connected by a complex regional system of roads修饰structures, 被路连接起来的只能是建筑，不能是房间
C each作rooms的同位语，房间被roads连接起来，不合逻辑
D scale of structures of rooms房间所拥有的建筑，建筑所拥有的规模，不合逻辑
E 两个句子没有连词

choice a is a run-on - it tries to have two main verbs without using any sort of subordinating element. if you take out modifiers, adjectives, etc., you're left with the following: the settlements were built with structures were connected. that's bad.

choice b is correct: it uses a nonessential modifier set off by commas ('of up to 600 rooms each'), which, if eliminated, yields the intact and legitimate sentence ...carefully engineered structures, connected by... (with another nonessential modifier).

choice c:
- 'scale of' doesn't make sense
- you can't say 'each that had...' (can't follow 'each' with a relative pronoun - if you're going to use a relative pronoun, it has to come directly after the thing it's trying to modify)
- no justification for using the past perfect ('had been') - that verb, if there's a verb there at all, should be in the simple past (the same tense as everything else in the sentence, because everything described in the sentence is contemporaneous)
- it doesn't make sense to use 'each' AFTER the comma, because it's not true that each structure was connected with a road system. instead, the road system connected all of the structures with each other, which is nowhere close to the same thing. (having 'each' BEFORE the comma makes sense, because it's actually true that each of the structures comprised up to 600 rooms.)
analogy:
the USA comprises 50 states, each of which is united by a federal government --> wrong (the implication is that each state has its own federal government)
the USA comprises 50 states, all of which are united by a federal government --> correct
the USA comprises 50 states, (all) united by a federal government --> correct, whether you have 'all' or not

choice d:
- 'scale of' doesn't make sense
- the use of AND sets up ostensible parallelism, but the two structures given aren't parallel (one starts with of and the other with with)

choice e is also a run-on sentence (you'll see this if you reduce it to its 'skeleton', a la choice a)

先看选项
AB和CDE的区别是： of more than 75 carefully engineered structures 是不是连着 of up to 600 rooms；
很明显of up to 600 rooms 是不能修饰前面的 structures （即便可以也会造成句子过分冗长，GMAT的出题人肯定不prefer这种答案）
排除CDE，剩下AB; A 两个谓语，排除；

整个句子的意思：查克峡谷的Anasazi居住地建造的规模宏大，有超过75个复杂的工程结构，每个工程结构都有超过600个房间，所有的工程结构之间由复杂的区域路径连接起来。
with表伴随用来进一步解释和补充spectacular scale（怎样的规模宏大？内部包含超过75个工程结构）。
connected with each other是作为modifier修饰structures的，所以不能加were。正确B
【补充】analogy:
the USA comprises 50 states, each of which is united by a federal government --> wrong (the implication is that each state has its own federal government)
the USA comprises 50 states, all of which are united by a federal government --> correct
the USA comprises 50 states, (all) united by a federal government --> correct, whether you have 'all' or not

Ron: https://www.manhattanprep.com/gmat/forums/the-anasazi-settlements-at-chaco-canyon-were-built-t2236.html
analogy:
the USA comprises 50 states, each of which is united by a federal government --> wrong (the implication is that each state has its own federal government)
the USA comprises 50 states, all of which are united by a federal government --> correct
the USA comprises 50 states, (all) united by a federal government --> correct, whether you have 'all' or not

排除法。A出现两个谓语，错。
C的each that这个句子是同位语，但是前边没有each可以同位的对象，错。D and前边找不到平行对象 E each had been是完整句子，跟前一个句子间无连词。只剩下B

each用法梳理：
each可以做代词、限定词、形容词或副词，
（1）作代词时，非物主代词的代词本身就是名词，后面不接名词，除非是名词形容词化的合成词，所以接名词时带上of等介词，A，each of 600 rooms，each作代词/名词，each of表示……的每一个，后面只能跟复数名词，同时该复数名词必须被限定，如each of the students正确，each of students错误；
（2）each作形容词，指每一个……，后面只能接单数名词，C，each that=each structure，；
（3）each作形容词时也可以放在复数名词后面，谓语动词用复数，如we each have our own office.

- 'scale of' doesn't make sense
- you can't say 'each that had...' (can't follow 'each' with a relative pronoun - if you're going to use a relative pronoun, it has to come directly after the thing it's trying to modify)
- no justification for using the past perfect ('had been') - that verb, if there's a verb there at all, should be in the simple past (the same tense as everything else in the sentence, because everything described in the sentence is contemporaneous)
- it doesn't make sense to use 'each' AFTER the comma, because it's not true that each structure was connected with a road system. instead, the road system connected all of the structures with each other, which is nowhere close to the same thing. (having 'each' BEFORE the comma makes sense, because it's actually true that each of the structures comprised up to 600 rooms.)
analogy:
the USA comprises 50 states, each of which is united by a federal government --> wrong (the implication is that each state has its own federal government)
the USA comprises 50 states, all of which are united by a federal government --> correct
the USA comprises 50 states, (all) united by a federal government --> correct, whether you have 'all' or not

A，双谓语，排除
C，each that作同位语，但是根据句意，不是600个房间被连接
D，and with不平行
E，句子间缺少连词，排除
B correct

AE. run-on
C. that在each后面，错误。且 it's not true that each structure was connected with a road system. instead, the road system connected all of the structures with each other.
D. each错误，且... and (scale) with ...错误

1.逻辑推理，是这个scale有75个结构，而不是75个结构的scale，所以CDE的句意都错
2.with+noun后面不能接谓语were，A错。
3.动词时态，had been是错的，DE错。

CHOICE A-run-on
CHOICE CDE- 'scale of' doesn't make sense
CHOICE C- you can't say 'each that had...' (can't follow 'each' with a relative pronoun - if you're going to use a relative pronoun, it has to come directly after the thing it's trying to modify)
CHOICE CE- no justification for using the past perfect ('had been') - that verb, if there's a verb there at all, should be in the simple past (the same tense as everything else in the sentence, because everything described in the sentence is contemporaneous)
CHOICE CE- it doesn't make sense to use 'each' AFTER the comma, because it's not true that each structure was connected with a road system. instead, the road system connected all of the structures with each other, which is nowhere close to the same thing. (having 'each' BEFORE the comma makes sense, because it's actually true that each of the structures comprised up to 600 rooms.)

A 两个谓语 错误
E runon
D and with each在前面找不到平行对象
C each是名词后面跟一个定语从句，该定语从句省略后只剩下一个名词

https://www.manhattanprep.com/gmat/forums/the-anasazi-settlements-at-chaco-canyon-were-built-t2236.html

A出现了两个谓语，错

each that。。。做同位语点时候没有指代，我以为可以指代前面的room。。。

with 和 of 是什么成分呀，each又是什么成分。。。。

C、each 是主语 that had been…是修饰each 的那就那样谓语，句子不完整了

有each出现，一定是关系到前面的某个复数名词。"comma + each" 都不对因为each不能指代comma前的复数名词，成了没有连词的独立句子。
C中and前后不平行。

- it doesn't make sense to use 'each' AFTER the comma, because it's not true that each structure was connected with a road system. instead, the road system connected all of the structures with each other, which is nowhere close to the same thing. (having 'each' BEFORE the comma makes sense, because it's actually true that each of the structures comprised up to 600 rooms.) 后面两句都是修饰structure。each意思不对。