Subject: mathqa
Question: the average age of 15 students of a class is 15 years . out of these , the average age of 4 students is 14 years and that of the other 10 students is 16 years . the age of the 15 th student is
Option: 
A: 21 years
B: 9 years
C: 9 years
D: 11 years
Answer: C