There are two bags, one of which contains 3 black and 4 white balls, while the other contains 4 black and 3 white balls. A dice is cast, if the face 1 or 3 tums up, a ball is taken from the first bag and if any other face turns up, a ball is chosen from the second bag. The probability of choosing a black ball is .........

A

$$\frac{11}{21}$$

B

$$\frac{10}{21}$$

C

$$\frac{12}{21}$$

D

$$\frac{9}{21}$$