IMO A
The question stem is asking for a conclusion that follows from the following facts.
1) No mathematician today would flatly refuse to accept the results of an enormous computation.
2) In the past some mathematicians rejected the results of a complex computer demonstration of a very simple mapping theorem
3) Some mathematicians still believe a simple theorem ought to have a simple proof.
4) Some simple theorem have required enormous proofs.
If 3) Some mathematicians still believe a simple theorem ought to have a simple proof and 1) No mathematician today would flatly refuse to accept the results of an enormous computation, then it would follow that some of those mathematicians who believe a simple theorem ought to have a simple proof would consider accepting the results of an enormous computation. Answer (A) states this.
Originally, I was wary of choosing this answer. Because the premise states that "no mathematician today..." I expected the answer to state "all mathematicians...would consider accepting" rather than "some mathematicians...would consider accepting".
After reading the premises a little closer I believe (A) is correct. The premise states that "no mathematician today would flatly refuse to accept the results of an enormous computation". I take it that this means that no mathematician would reject a result solely because it was derived from an enormous computation. However, they may reject the result for other reasons. This distinction allows for some of them to consider accepting a result and while some of them do not consider accepting the result.
B, C, D, and E discuss, in one way or another, what non-mathematicians believe. The fact set provided does not discuss the beliefs of non-mathematicians.