Month sequence pattern (X and Y)

Convert the months into their numerical equivalents (1 to 12): 1, 1, 12, 10, X, 3, 10, Y, 9. Check the differences between consecutive terms, applying modulo 12 math (where moving backwards from 1 loops to 12): 1 to 1: Diff = 0 1 to 12: Diff = -1 12 to 10: Diff = -2 The pattern of differences is a decreasing arithmetic progression: 0, -1, -2, -3, -4, -5, -6... Applying -3: 10 - 3 = 7 (July). So X is July. Applying -4: 7 - 4 = 3 (March). Matches sequence! Applying -5: 3 - 5 = -2, which modulo 12 is 10 (October). Matches sequence! Applying -6: 10 - 6 = 4 (April). So Y is April.

Answer: (b).