Let $x = r \cos \theta$ And $y = r \sin \theta$

Multiple Choice

Let $x = r \cos \theta$ and $y = r \sin \theta$ Then $\frac { \partial ( x , y ) } { \partial ( r , \theta ) }$ is

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