Answer is option C] processor can't be preempted.
Why?
I assume that you know about Assembly Language. Whatever you see executed on PC, is nothing but instructions. These instructions are predefined and known to processor (ex : Intel P4, core2 Duo, i5, i7 they differ because of instruction set) .
In certain cases to avoid race conditions, atomic(indivisible) operations are preferred. and these indivisible operations are executed in one clock cycle. Hence Even if there is preemption, Operation is finished in that clock cycle only.