8, 11, 21, 15, 18, 21, 22, ... choose which pair of numbers comes next?

A. 25, 18

B. 25, 21

C. 25, 29

D. 24, 21

E. 22, 26

Answer: Option B

Solution(By Examveda Team)

This is an alternating addition series, with a random number, 21, interpolated as every third number. The addition series alternates between adding 3 and adding 4. The number 21 appears after each number arrived at by adding 3.