GMAT Sentence Correction (SC) | The success of the program to eradicate smallpox has

The success of the program to eradicate smallpox has stimulated experts to pursuewhat they had not previously considered possible -- better control, if not eradication, of the other infections such as measles and yaws.
A. what they had not previously considered possible -- better control, if not eradication, of the other infections such as
B. what they had not previously considered a possibility -- better control, if not eradication, of such infections like
C. something they had not previously