9, 12, 11, 14, 13, ?, 15	Choose the correct choice from the following choices
A) 12  B) 16  C) 15  D) 17  E) 10
Alternatively, 3 is added and one is subtracted.   Answer : 16.
<result>B</result>
9, 12, 11, 14, 13, ?, 15