Which of the following is an example of empirical probability?

A. There are 24 chocolates in a box, and 13 of them have nuts. The probability a chocolate has nuts is 13/24 .

B. Sara put 5 black marbles and 3 white marbles in a bag. The probability of selecting a black marble is 5/8 .

C. There are 13 songs on a CD, and 4 of them are hip-hop. The probability a randomly selected song is hip-hop is 4/13.

D. Nick tried a skateboard trick 7 times and succeeded 2 times. The probability of success is 2/7.