In following question,a number series is given with one term missing. Choose the correct alternative
9 , 12 , 11 , 14 , 13 , x , 15
11 * 1 / 9, 12 * 1 / 2, 14 * 2 / 7, 16 * 2 / 3,
5, 6, 7, 8, 10, 11, 14,
(2, 3), (3, 5), (5, 7), (7, 11), (11, 13),
2 , 4 , 12 , 48 , 240 , x