What will come in place of question mark(?) in the following series?
X5C, U8F, ?, O17L, L23O

Information Given:
Series: X5C, U8F, ?, O17L, L23O

Logic:
1st letter: −3 each step
Number: +3, +4, +5, +6
3rd letter: +3 each step

Step-by-step:
1st letters: X → U (−3) → R (−3) → O → L ✔
Numbers: 5 → 8 (+3) → 12 (+4) → 17 (+5) → 23 (+6) ✔
3rd letters: C → F (+3) → I (+3) → L (+3) → O (+3) ✔

Missing term = R12I

Final Answer:
R12I

Final Correct Option:
(B)