Look at this series: 31, 29, 24, 22, 17, ... What number should come next?  Pick one
A) 11	B) 15	C) 16	D) 17	E) 18
15   15   This is a simple alternating subtraction series, which subtracts 2, then 5.
<result>B</result>
Look at this series: 31, 29, 24, 22, 17, ... What number should come next?