Choose the missing terms out of the given alternatives : Y, B, T, G, O, ?

The missing term is M.

The sequence is a simple substitution cipher, where each letter is replaced by the letter three places after it in the alphabet. So, Y becomes B, B becomes T, T becomes G, G becomes O, and O becomes M.

A. N is incorrect because N is not three places after M in the alphabet.
B. M is correct because M is three places after O in the alphabet.
C. L is incorrect because L is not three places after O in the alphabet.
D. K is incorrect because K is not three places after O in the alphabet.