Be sure to proof your question, you are missing some words. I'm assuming that A, B, and C include "is" if B or C do not that's ok there are other splits that rule them out.
Here's the way I went through this.

- I didn't see any glaring mistakes in the original (not that I'm fabulous enough at SC to notice all mistakes all the time) so I moved to the answers and used them as a guide.

- I split the choices and noticed D and E (assuming you copy and pasted correctly) begin with "a specially...." This is a run-on...needs a verb. "Sulfur D is a serious..." This would be the construction. These choices appear to be introducing another modifier but they do not. Elim D&E

- Among A, B, and C "because of" VS "because it" we're talking about Sulfur D here so we would say "Sulfur D is bad because it does x..." not "Sulfur D is bad because of doing something..." elim B

- A VS C - Idiom for capable is "X is capable of Y" Choice C seems akward. Choice A the Idiom for ability is "X's ability to Y" This seems more clear. Try cutting off all that crap before and replace "it" with Sulfur D. "Sulfur D diminishes the respiratory system's ability to deal..." vs "Sulfur D diminishing the respriratory system's capability of dealing..." Ugh...Does that make sense to you?? Elim C

Hope that helps.

yeah u r correct "is" is not in the underlines portion of the original question.

but if this is so..then how did u elimate D

moreover D and A sounds the same to me.

One reason for choosing A over D is because of wordiness.

system's capability is better that capability of system.

Another reason is especially v/s special. I think adverb is needed instead of an adjective. Will be happy if someone can expand on this.

If you look carefully then you'll see that
option A as well as D consists of specially and especially so both are adverbs.

and about wrdiness a contains the appostrophie "'s" which is actually we can say less preferred.

can you give any other reason to eliminate D.

Hi guys, let's see if I can clear up any confusion between (A) and (D) .

Note the word 'especially' in (A). 'Especially', as used in the sentence, means to a great extent/particularly.

Now, notice the word 'specially' in (D). 'Specially', in written English, cannot mean to a great extent. Let's compare:

Correct: He was especially adept at standardized tests, usually scoring in the top 10%.

Incorrect: He was specially adept at standardized tests, usually scoring in the top 10%.

Therefore (D) is out and (A) is the answer.

Hi Chris,

Thanks for your inputs.

I have looked into dictionary and found both words to have same meaning!

Can you site few examples that sheds more light on usage of the words?