If a and b are unique prime integers, which of the following must be even?
Options:
(A) a−b
(B) a−2b
(C) 2a−2b
(D) 2a−b
(E) ab^2 Think first, then make a decision. Some random thoughts:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Let's assume that a is an even prime integer and b is an odd prime integer, their subtraction results in an odd integer and an odd integer multiplied by an even integer yields an even integer. So the answer is (C).