How Many Nth-Order Partial Derivatives Does a Function of Two $n ^ { 2 }$

Multiple Choice

How many nth-order partial derivatives does a function of two variables have?

A) $n ^ { 2 }$
B) $2 ^ { n }$
C) $2 n$
D) $\frac { n } { 2 }$
E) $n 2 ^ { n }$