$13,17,19, 23$ all are prime numbers, and our pattern is prime number plus two. So it will be $15,19,21,25.$
- $15^{\text{th}}$ alphabet $M$
- $19^{\text{th}}$ alphabet $Q$
- $21^{\text{th}}$ alphabet $S$
- $25^{\text{th}}$ alphabet $Y$
So, the correct answer is $(A).$