Look at each choice.
A. Team A has 15 players. 4 are 8 years old. This probability is 4/15. 4/21 is false.
B. Team C has 16 players. 8 of them are 8 years old. This probability is 8/16 = 1/2. 16/21 is false.
C. Team C has 16 players. 5 of them are 10 years old. This probability is 5/16. 5/16 is true.
D. Team B has 13 players. 3 of them are 10 years old. This probability is 3/10. 13/58 is false.