Question

Twenty-three students wrote a statistics examination having a maximum of 50 marks. The mark distribution is given in the following stem-and-leaf diagram:

0 9
1 25
2 01335889
3 001369
4 02248
5 0

Q1 is equal to:
a) 15
b) 21
c) 23
d) None of the above

THE ANSWER IS: C

Please Explain why. Greatly appreciated.