SHTG
GXHW
GTHS
STHO
Answer is Wrong!
Answer is Right!
The correct answer is (a) SHTG.
The series is a simple substitution cipher, where each letter is replaced by the letter three places after it in the alphabet. So, A becomes Z, B becomes Y, C becomes X, and so on.
The first three letters of the series are AZBY. If we replace each letter with the letter three places after it in the alphabet, we get SHTG.
Therefore, the next letter in the series is SHTG.
The other options are incorrect because they do not follow the pattern of the series.