Assume That Height Is a Function of Age and That $H=f(a)$

Assume that height is a function of age and that $H=f(a)$ is the average height (in inches) for females in the US at age $a$ years. What is the practical interpretation of $f(z) +10$ ?

A) $z$ plus the number of US females who are 10 inches tall.
B) 10 plus the number of US females who are $z$ inches tall.
C) 10 years older than the average US female who is $z$ inches tall.
D) 10 inches taller than the average height of a $z$ year old US female.