Find the odd letter cluster out of the given alternatives.

Correct option is B

​$$\begin{aligned}\text{(a)} \quad I \xrightarrow{+2} K \xrightarrow{+2} M \\\text{(b)} \quad G \xrightarrow{-2} E \xrightarrow{-2} C \\\text{(c)} \quad O \xrightarrow{+2} Q \xrightarrow{+2} S \\\text{(d)} \quad U \xrightarrow{+2} W \xrightarrow{+2} Y \\\end{aligned}$$​​