For a rational number r, if we add 3 to its denominator it is $$\frac{1}{3}$$ and if we add 4 to its numerator it is $$\frac{3}{4}$$. Then r =

A

$$\frac{3}{7}$$

B

$$\frac{4}{9}$$

C

$$\frac{5}{12}$$

D

$$\frac{7}{15}$$