There are two balls in an urn. Each ball can be either white or black. If a white ball is put into the urn and there after a ball is drawn at random from the urn, then the probability that it is white is

A

$$\frac{1}{4}$$

B

$$\frac{2}{3}$$

C

$$\frac{1}{5}$$

D

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