cde用的是unlike不平行，先排除
b 后半句中competing companies one day may be partners。   one day修饰company语意有问题。
并且看到a选项中是companies that compete，ab发生词顺序调换，要着重思考与调换顺序的词相连接的为划线部分，此句即为one day。语意是想说一时是竞争对手彼时是合作伙伴，所以one day应该是修饰竞争这个含义的，a正确b明显错误

a 用的是whereas，比较的是句子
Difference between unlike/whereas:
Unlike must compare nouns
Whereas must compare clauses

In the correct answer choice, we're not comparing prepositional phrases, we are comparing clauses:

Whereas lines of competition are clearly defined (in the more established industries), (in the Internet industry) they are blurred and indistinct...

This would be similar to:

Whereas John is crazy on his vacations, at his house he is prim and proper.

as 引导从句

unlike， like 对比的对象属性要一致

曼哈顿RON大神说答案是A诶，B前面半句没问题，就是one day不能修饰名词company.  A不存在lines of competition和Internet industry不可比的问题，因为Whereas的比较是句子和句子的比较，不是名词和名词，也不是介词和介词的比较，Whereas lines of competition are clearly defined和they are blurred and indistinct对比正确，没有问题；the more established industries没有歧义，注意前面有定冠词the,就是industries that are more established这一个意思，还比较简介

B one day是修饰adv. 不可以修饰名词 曼哈顿论坛的老师说的，A是正确的

If you see the order of elements in a sentence switched between choices, think about WHAT DESCRIBES WHAT ELSE.
In making this decision, you may need to look at non-underlined words that are adjacent to the words undergoing the switch.

Here, some answer choices contain "competing companies". Others contain "companies that compete", switching those two elements.
This distinction should call your attention to the neighboring phrase "one day""”which can only sensibly describe competition, not the companies themselves.

正确答案坑定是A， B很明显很wordy

A． more established industries，more有同时修饰established和industries的歧义
B． 正确
C． Unlike前后比较应该使用同种性质的词语
D． they在优先指代more established companies，而不是在指代lines of competition，此处where引导的定语从句在两个逗号之间，视为插入，可以忽略。
E． those在优先指代more established companies，而不是在指代lines of competition，此处with引导的定语在两个逗号之间，视为插入，可以忽略。