31, 29, 24, 22, 17, ?
Choose the correct choice from the following answers:
A) 12 B) 14 C) 15 D) 17 E) 20
15   15   This is a simple alternating subtraction series, with a pattern -2, -5, -2, -5 ....
<result>C</result>
31, 29, 24, 22, 17, ?