1.  In alphabet series, some alphabets are missing which are given in that order as one of the alternatives below it. Choose the correct alternative : aa _ aaa _ aaaa _ aaaa _ b

A. baaa
B. bbaa
C. bbbb
D. bbba

Answer: Option D

Explanation:

The series is aab / aaab / aaaab / aaaaab.

Thus, the number of a`s is increasing by one in the successive sequence.