What should replace the question mark in the following series, based on…

Concept

In an alphabet series, compare letters that occupy the same position in consecutive groups.

Convert letters to their alphabetical positions and apply the same fixed shift at each position, wrapping from Z back to A.

Application

1. First position: S → X → C → H. Each move is +5 letters, so H + 5 = M.

2. Second position: W → B → G → L. Each move is +5 letters, so L + 5 = Q.

3. Third position: U → Z → E → J. Each move is +5 letters, so J + 5 = O.

4. Fourth position: N → S → X → C. Each move is +5 letters, so C + 5 = H.

Cross-check and contrast

Applying a +5 shift to every letter of HLJC gives MQOH; shifting every letter of MQOH back by 5 returns HLJC.

• MOHQ corresponds to the position-wise shifts +5, +3, −2, and +14 from HLJC.

• MHYU corresponds to the position-wise shifts +5, −4, +15, and +18 from HLJC.

• MQOH corresponds to the position-wise shifts +5, +5, +5, and +5 from HLJC.

• MQSW corresponds to the position-wise shifts +5, +5, +9, and +20 from HLJC.

Therefore, the missing group is MQOH.