Find the odd set of letters from the given alternatives.

Correct option is C

​$$W \xrightarrow{-2} U \xrightarrow{-2} S$$​​

​$$Q \xrightarrow{-2} O \xrightarrow{-2} M$$

$$G \xrightarrow{+2} I \xrightarrow{+2} K$$

$$E \xrightarrow{-2} C \xrightarrow{-2} A$$​​​​