Here's the
official explanation provided by the GMAC for this question:
This sentence describes pharmacologists concluding that an amalgam of Chinese and Western medicine is probably equal or superior in quality to any other treatment system. In each option this comparison is expressed using two alternatives, one including the word
good and the other including the word
better, with the latter bracketed by commas. These alternatives must both be adjectival modifiers and parallel in form. The portion of the sentence outside the phrase in bracketing commas must be grammatical. If the amalgam of Chinese and Western medicine is itself one of the systems being considered, the comparison should strictly be between it and any other system, not
any system; otherwise the amalgam is being compared to itself as well as to other systems.
Option A: The phrase
as good must be followed by
as when used between two noun phrases. When the phrase
or better than and its bracketing commas are removed from the sentence, the surrounding phrase
as good any system is ungrammatical. If the amalgam is itself one of the systems being considered, the phrase
any system oddly suggests that the amalgam is being compared to itself as well as to other systems.
Option B: The phrase
as good must be followed by
as, not
than, when used between two noun phrases. When the phrase
or better and its bracketing commas are removed from the sentence, the surrounding phrase
as good than any system is ungrammatical. If the amalgam is itself one of the systems being considered, the phrase
any system oddly suggests that the amalgam is being compared to itself as well as to other systems. The word
being is unnecessary.
Option C: When the phrase
or better than and its bracketing commas are removed from the sentence, the surrounding phrase
as good any system is ungrammatical. If the amalgam is itself one of the systems being considered, the phrase
any system oddly suggests that the amalgam is being compared to itself as well as to other systems. The words
which are being are unnecessary. Furthermore, since patients are people, the more appropriate relative pronoun to use for them would be
who, not
which.
Option D: In formal writing, the phrase
good as should be preceded by
as when used in a comparative sense between two noun phrases.
Option E: Correct. The phrases
as good as and
better than are parallel in form, and each works grammatically between two noun phrases. The amalgam is appropriately compared only to other systems, not to itself. The phrasing is concise, with no unnecessary words following
patients.
The correct answer is E.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.