Distinct points P, Q, R, and S lie on the circle x^{2}+y^{2}=25 and have integer coordinates. The distances P Q and R S are irrational numbers. What is the greatest possible value of the ratio \dfrac{P Q}{R S} ?

**Answer Choices**

A. 3

B. 5

C. 3 \sqrt{5}

D. 7

E. 5 \sqrt{2}