1. 

In the following question, a letter series is given. Some of the letters of the series are missing. This missing letters are given in same order as one of the four/five alternatives below the series. Find out the correct alternative.

adb__ac__da__cddcb__dbc__cbda
A. bccba
B. cbbaa
C. ccbba
D. bbcad

Answer: Option B

Explanation:

Pattern of the series as shown below

adbc/acbd/abcd/dcba/dbca/cbda => cbbaa

Hence, the missing letters are cbbaa.