Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the letter-cluster that is different.
(Note: The odd one out is not based on the number of consonants/vowels or their position in the letter cluster.)

The correct option is CWSR.

To find the odd letter-cluster out, let us analyze the positional values of the letters in the English alphabet for each option:

1. KEAY:
• K = 11
• E = 5 (11 - 6 = 5)
• A = 1 (5 - 4 = 1)
• Y = 25 (1 - 2 = -1 ≡ 25 mod 26)
Pattern: -6, -4, -2

2. SMIG:
• S = 19
• M = 13 (19 - 6 = 13)
• I = 9 (13 - 4 = 9)
• G = 7 (9 - 2 = 7)
Pattern: -6, -4, -2

3. MGCA:
• M = 13
• G = 7 (13 - 6 = 7)
• C = 3 (7 - 4 = 3)
• A = 1 (3 - 2 = 1)
Pattern: -6, -4, -2

4. CWSR:
• C = 3
• W = 23 (3 - 6 = -3 ≡ 23 mod 26)
• S = 19 (23 - 4 = 19)
• R = 18 (19 - 1 = 18)
Pattern: -6, -4, -1

All letter-clusters except CWSR follow the pattern of subtracting 6, 4, and 2 sequentially between consecutive letters. Therefore, CWSR is the odd one out.