1.  2 3 4 5 6 4 8
A. 9 10
B. 4 8
C. 10 4
D. 9 4
E. 8 9

Answer: Option D

Explanation:

This is an alternating addition series with a random number, 4, interpolated as every third number. In the main series, 1 is added, then 2 is added, then 1, then 2, and so on.