Concept:Each term consists of two letters. The first letter advances by two steps, and the second letter recedes by one step.Explanation:Look at the first letters: A, C, E. Each increases by 2 (A+2=C, C+2=E), so the next first letter is E+2=G.Look at the second letters: Z, Y, X. Each decreases by 1 (Z-1=Y, Y-1=X), so the next second letter is X-1=W.Combining gives GW.
