Here the letter series is as follows :-
ncd/ dcn
After using the pattern the complete letter series will be as below.

Correct Option: C

Here the letter series is as follows :-
ncd/ dcn
After using the pattern the complete letter series will be as below.
ncd / dcn / ccd / dcn / ndd / dcn / ndd

As per given question, the letter series is following the below pattern.
a b a b c
After using the pattern the complete letter series will be as below.

Correct Option: D

As per given question, the letter series is following the below pattern.
a b a b c
After using the pattern the complete letter series will be as below.
a b a b c /bc bc a/ caca b

In each subsequent term the last letter becomes the first letter.

Correct Option: B

In each subsequent term the last letter becomes the first letter.
Using the same pattern, we will get next term of given letter series.
bcde ebcd debc cdeb bcde

As per given question, the letter series is following the below pattern.
a b c d d
After using the pattern the complete letter series will be as below.

Correct Option: B

As per given question, the letter series is following the below pattern.
a b c d d
After using the pattern the complete letter series will be as below.
a b c d d/ a b c c d/ a b b c d/ a

The given letter series in below pattern.
ccba
Using the same pattern, we will get complete letter series.

Correct Option: B

The given letter series in below pattern.
ccba
Using the same pattern, we will get complete letter series.
ccba/ b b ca/ a a bc/ cc b a/ b