The underlined part must be started with "natural gas" because natural gas is the subject of this sentence. So, D, E out
The intended comparison, between two options metioned here, is to be established through correct idom - "than". Only A has that correct idom. B,C OUT
A is the answer.

The sentence has two split to consider. Option A has the correct implications.

HTH

The beginning of the sentence requires "natural gas" for the start (what was widely used to fuel home heating systems?). A,B,C are left. B is really bad because it states that natural gas did all that stuff as oil (so natural gas can be oil?). C is missing a comparison word (natural gas did less...where's the than?). So A is left.

Dear Mbawarrior01

I'm happy to respond.

Here is a very difficult to appreciate fact about the official questions. The official questions, in GMAT Prep or the OGs, are former live GMAT questions. In order to get onto the live GMAT, questions undergo an extensive statistical evaluation, from which many questions are weeded out. Once a question is on the GMAT, it continues to accumulate an extraordinary amount of data. Then, some of these questions, the ones that have done well, are released and put in the OG or in GMAT Prep. At this point, these are some of the highest quality test questions on earth! Each questions has tens of thousands of data points behind it assuring its quality.

By contrast, the explanations were written once by somebody, maybe a starving graduate student, and so far as I can tell, they have undergone almost no feedback whatsoever. A few are excellent, many are OK, and some are atrocious.

Now, the deceptive thing is that the questions and the explanations are all bundled together, whether in GMAT Prep or the OG, all in the same font and format, so that it may appear to the naive reader that they are of the same quality. They are NOT!

Keep this in mind. Here's a text version of the question:
Though widely used for decades to fuel home heating systems, utility boilers, and industrial furnaces, natural gas has accounted for far less of the energy consumed in the United States than has oil.

A. natural gas has still accounted for far less of the energy consumed in the United States than has oil
B. natural gas has still accounted for far less of the energy consumed in the United States as oil
C. natural gas still has accounted for far less of the energy consumed in the United States as oil has
D. still far less of the energy consumed in the United States has been accounted for by natural gas as by oil
E. still far less of the energy consumed in the United States has been accounted for by natural gas than has oil

First of all, the problem that simply torpedoes (B) is the idiom blunder, "less ... as." That should be front and center in any discussion of why (B) is wrong. There is, though, something else going on, to which the explanation refers.

See this post:
4 Challenging Comparison Questions on the GMAT
In that post, I explain the difference between what I call a subjective comparison and objective comparison.

If we changed (B) and replaced the word "as" with the word "than," we would have corrected the idiom problem but we would still have the logical problem. In particular, the sentence would leave unclear whether "oil" was intended to be a subjective comparison or an objective comparison.

Read that blog carefully, and I think what the official explanation was trying to say will make more sense.

Mike
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