Question: If the point $(3,6)$ is on the graph of $y=g(x)$, and $h(x)=(g(x))^2$ for all $x$, then there is one point that must be on the graph of $y=h(x)$. What is the sum of the coordinates of that point?
A: 3
B: 6
C: 39
D: 36
Please eliminate two incorrect options first, then think it step by step and choose the most proper one option.