Look at this series: 21, 9, 21, 11, 21, 13, 21, ... What number should come next?
Options:
(A) 15
(B) 14
(C) 17
(D) 18
(E) 19 Stream of consciousness:
In this alternating repetition series, the random number 21 is interpolated every other number into an otherwise simple addition series that increases by 2, beginning with the number 9.
Thus, the answer is (A).