Select the option that is related to the third term on the same basis as the second term is related to the first term.
ACT : BFY :: BAD : ?

Given: ACT : BFY :: BAD : ?

Logic: 1st letter + 1 = 4th letter, 2nd letter + 3 = 5th letter, and 3rd letter + 5 = 6th letter

For, ACT : BFY

A + 1 = B, C + 3 = F, T + 5 = Y

Similarly,

BAD : ?

B + 1 = C, A + 3 = D, D + 5 = I

So, BAD : CDI

Thus, correct option is (b).