I've attached the problem.
The answer is D. I thought it would be C. I do not see how it could be D.
But it is wrong. WHY?
Well, we do not know that those two lines intersect at the center of the circle.
It looks like they in fact do.
But looks are deceiving.
That information is not given in this question.
You must realize that the ‘Graduate Record Exam’ is designed to measure how well one is prepared to do graduate level work. We do not want graduate students to work on the basis of what ‘appears to be the case’, but we want the graduate student to act upon what is known to be the case.
Grr I hate it when they do that. Another question had shown a right triangle (but not stated it was) and then said each of the bases is 1... so immediately I said, oh, well the hypot then is the sqrt(2)... but D was the answer again. Stupid. Why try trick people? That doesn't measure intelligence.
Ok, so lets assume that these lines do not meet in center. If this is the case, then how can opposite regions be equal? Unless you can't even assume that those are straight lines... bizarre.
And the question is fine. You might view it as a "trick" question, but they really just want to see if you can think critically and not take anything for granted. They tell you up front what you can and cannot assume (IIRC all you get is that all numbers are real). Remind yourself at the beginning of every problem with a picture that it is NOT drawn to scale.
EDIT: If it makes you feel any better, I got an 800 on the GRE Quant and I suspect there is a good chance I would have hastily marked C too if this had been a question