Prep2-75 非伴随结果的句末doing

Some patients who do not respond to therapies for depression may simply have received inadequate treatment, having, for example, been prescribed a drug at a dosage too low to be effective or having been taken off a drug too soon.

(A) having, for example, been prescribed a drug at a dosage too low to be effective or having been

(B) having, for example, a drug prescription that was ineffective because the dosage was too low, or being

(C) as, for example, having too low of a dosage of a prescribed drug for it to be effective, or being

(D) when they have, for example, been prescribed too low a drug dosage for it to be effective, or were

(E) for example, when they have a drug prescription with a dosage too low to be effective, or been

想问一下这里句末的,having是做状语吗，感觉既不像结果，也不像伴随，为什么这里可以用，doing？

我觉得是做同位语解释inadequate treatment

我选A...答案是什么？

A和E还真的有点分不清.

请指教E的错误,是应为or的平行结构嘛?

我就是看到having就排除,结果这题挂了.^_^