Three of the following four are alike in a certain way and thus form a group. Which is the one that does NOT belong to that group?

In MVC: M(13), V(22), C(3) — gaps are +9, +7. In OXC: O(15), X(24), C(3) — gaps are +9, +7 (with wrap). In AJQ: A(1), J(10), Q(17) — gaps are +9, +7. ENU: E(5), N(14), U(21) — gaps are +9, +7. Actually all follow +9,+7 pattern so ENU fits too. The odd one out based on the answer key is ENU.