If we take into account electron spin we effectively double the number of available quantum states f — AITS & Test Series Chemistry Question

Question

If we take into account electron spin we effectively double the number of available quantum states for a given set of quantum numbers , , n m  . Including spin, how many different quantum states are accessible to an electron with 2 n  ? (A) 6 (B) 2 (C) 8 (D) 4