Which letter-cluster will replace the question mark (?) to complete the given series?
RWIC, OUFG, ?, IQZO, FOWS

Correct option is D

Given: RWIC, OUFG, ?, IQZO, FOWS
In the given word RWIC, OUFG
First Letter: R (18th letter) to O (15th letter): 18 - 3 = 15
Second Letter: W (23rd letter) to U (21st letter): 23 - 2 = 21
Third Letter: I (9th letter) to F (6th letter): 9 - 3 = 6
Forth Letter: C (3rd letter) to G (7th letter): 3 + 4 = 7
Logic: The Letter are decreased by 3, 2, 3 and increased by 4. OUFG, ?,
First Letter: O (15th letter): 15 - 3 = L (12th letter)
Second Letter: U (21st letter): 21 - 2 = S (19th letter)
Third Letter: F (6th letter): 6 - 3 = C (3rd letter)
Forth Letter: G (7th letter): 7 + 4 = K (11th letter)
Correct answer is (d) LSCK.