Three of the following four letter-clusters are alike in a certain way and one is different. Pick the odd one out.

(NOTE: The odd one out is not based on the number of vowels or consonants in the word)​​

Logic:  4th letter + 1 = 3rd letter for all options:

Option A: IOSR

R + 1 = S (Correct).

Option B: UCGF

F + 1 = G (Correct).

Option C: WAED

D + 1 = E (Correct).

Option D: HEIS

S + 1 = I (Incorrect, should be T).

Option D (HEIS) is the odd one out.