Explanation:

To find the odd one out, we analyze the relationship between the letters in each pair based on their alphabetical positions (A=1, B=2, ..., Z=26). For SO: S is the $19^{\text{th}}$ letter, O is the $15^{\text{th}}$ letter. The difference is $19 - 15 = 4$. For ME: M is the $13^{\text{th}}$ letter, E is the $5^{\text{th}}$ letter. The difference is $13 - 5 = 8$. For PL: P is the $16^{\text{th}}$ letter, L is the $12^{\text{th}}$ letter. The difference is $16 - 12 = 4$. For KG: K is the $11^{\text{th}}$ letter, G is the $7^{\text{th}}$ letter. The difference is $11 - 7 = 4$. We observe that in options (1) SO, (3) PL, and (4) KG, the difference between the alphabetical positions of the two letters is $4$. However, in option (2) ME, the difference is $8$. Therefore, ME is the odd one out. Options (1) SO, (3) PL, and (4) KG are similar with a consistent difference of $4$ between their letter positions.