Select the number from the given options that can replace the question mark (?) in the following series.
6, 11, 8, 9, 11, 7, ?, 5

Correct option is B

Let's analyze the given series: 6, 11, 8, 9, 11, 7, ?, 5
We can split the series into two alternating patterns:
First pattern (1st, 3rd, 5th, and 7th terms):
6, 8, 11, ? This pattern increases by 2, 3,4,…:
6 + 2 = 8
8 + 3 = 11
11 + 4 = 15
Second pattern (2nd, 4th, 6th, and 8th terms):
11, 9, 7, 5 This pattern decreases by 2 each time:
11 - 2 = 9
9 - 2 = 7
7 - 2 = 5
Therefore, the missing number in the series is 15.
Alternative method:

Final answer is 15.