45 children attend a preschool. The number of 2 year olds is one half the number of 3 year olds. The number of 4 year olds is the same as the number of 3 year olds.

A. How many 2 year olds attend preschool
B. How many 3 year olds attend preschool
C. How many 4 year olds attend preschool