The correct option is
A CLL
The difference between position of 'C' and 'D' is 1, between position of 'A' and 'D' is 3, between 'T' and 'Y' is 5.Same relation is satisfied by BIG option A
Difference between position of 'B'and 'C' is 1, between 'I'and 'L' is 3, between 'G'and 'L' is 5.