I vote for C.
I'll explaining. Please let me know if it is incorrect.
Let the number of ppl who request for brochure be X
Let the number of ppl who applied to that MBA Program: x/2
(1) Twenty percent of those who apply are extended offers of acceptance
.2*(x/2)=x/10 are given offers.But we do not know if they enrolled or not.So A is not sufficient.
(2) Fifty percent of those who receive offers enroll in a different MBA program
We do not know the number who receive offers. So,B is not sufficient.
Let us take statement 1 and 2.
Thus, students who received offers but did not join the MBA program:
Thus, we would get the number of persons who eventually enrol.
(Paul: I made an assumption here that fron all those who were offered admissions,they either went for this MBA program or a different one.
No body backed out and decided not to do an MBA this year.
510 on my first GMAT. 610 on second GMAT.!
The struggle continues.