Could it be B?
We know 1*2*3*4*5*6*7*8 is a multiple of a^n and with n=6, the only option is 2^6
I agree that a^n, w/ n=6 that a can only be 2.
However, I fail to see anywhere in the original stem relating a to n.
All S2 says is n=6. The original stem says that a & n are + integers. Nothing more about a & n. It does say that a is divisble by 8! or 8! is a multiple of a.
I cannot see how B is correct. A as well, I don't see how it can't be correct as pointed at by JBS.
So i would go w/ C.