This series interleaves two patterns. Odd positions (1,3,5,7): 2, 13, 12, 11. Even positions (2,4,6,8): 15, 12, 11, ?. The even sequence shows: 15→12 (-3), 12→11 (-1). If the pattern continues as -3, -1, -3, -1, then 11-3=8. If it's -3, -1, 0, then 11-0=11. Option A (11) suggests the even sequence stabilizes at 11, matching the odd sequence's end. Both sequences converge to 11.