i think the original sentence's meaning is stressing the "cost of illiteracy" is at least 20billion where as E changes the meaning to "because of illiteracy" 20billion are lost

IMO C

This question disturbs my life. I read the book "element of style" and " ten lessions in style" which said that if we use verb, the sentence is more direct and vigorous. you can read about norminalization but do not read too much, dont stray away from gmat

this is a problem of style, DIRECT AND VIGOROUS.

now, read the OG explanation, which normally is not clear

"make sentence more direct is to focus on subject and verb..."

"use of cost as a verb eliminates prepositional phrase..."

the lesion of this is that

1, what agent should be subject and verb in a sentence so that the sentence is direct, what is focus of interest. focus of interest decide what is subject and verb. see Q 203 in OG10

2, use verb to avoid prepositional phrase, making the sentence more direct (you can see the question 'irigation required by new variety..." Q 128 in OG10 and OG11 for this point)

Ron, Stacey, Stuart, pls,help us with this.

"Because" is not preferred by GMAT. So if you have a correct choice with "Because" and one without , then go for the one that does not use "Because".

I think very simplistically speaking C, clearly illucidates the fact the oppurtunity cost (i.e the losses suffered due to illiteracy ) costs the US X bn a year through - lost industrial o/p etc... while option E messes up the meaning completely - its states that the losses in industrial o/p have cost x bn which is not true.

The intention is very clearly articulated in C .

I think very simplistically speaking C, clearly illucidates the fact the oppurtunity cost (i.e the losses suffered due to illiteracy ) costs the US X bn a year through - lost industrial o/p etc... while option E messes up the meaning completely - its states that the losses in industrial o/p have cost x bn which is not true.

The intention is very clearly articulated in C .