A body of weight 30 N rests on a horizontal floor. A gradually increasing horizontal force is applied to the body which just starts moving when the force is 9 N. The coefficient of friction between the body and the floor will be

A

$$\frac{10}{3}$$

B

$$\frac{3}{10}$$

C

$$\frac{1}{3}$$

D

$$\frac{1}{9}$$