请教 老PREP(SC2)-39---终于找到资料弄懂了，求删

clisalong

As it is with traditional pharmacies, on-line drugstores rely on prescriptions to be successful, since it is primarily prescriptions that attract the customers, who then also buy other health-related items.

(A) As it is with traditional pharmacies, on-line drugstores rely on prescriptions to be successful

(B) As with the case of traditional pharmacies, on-line drugstores rely on prescriptions to have success

(C) As is the case with traditional pharmacies, prescriptions are the cornerstone of a successful on-line drugstore

(D) As traditional pharmacies, so on-line drugstores rely on prescriptions to be successful

(E) Like traditional pharmacies, the cornerstone of a successful on-line drugstore is prescriptions

我已经看过很多资料，但是还有一丝疑惑。下面这个是之前同类的帖子的回复。

as is the case with中as和so一样是指代一个situation，as is the case with可以看作一个平行结构。
其实C像下面这样写也没有语法错误，而且也包含了原句要表达的意思：
As prescriptions are the cornerstone of successful  traditional pharmacies, they are of a successful on-line drugstore...
只是这样写有歧义，as可以引导原因状语从句，显得好像前者是后者成立的原因，而且这个结构不如as is the case with简洁。

-- by 会员 aeoluseros (2011/5/2 2:43:37)

而我疑惑的是 as is the case with 的这个平行结构的对比对象是否要求概念相等？如题目中的，traditional paharmacies 这个是药店，而prescription是处方。我始终认为这两者不是概念不对等。请赐教！！！