In Changing from Cartesian to Polar Coordinates $\frac { \partial u } { \partial x }$

Multiple Choice

In changing from Cartesian to polar coordinates, $\frac { \partial u } { \partial x }$ is

A) $\sin \theta \frac { \partial u } { \partial r } + \cos \theta \frac { \partial u } { \partial \theta } / r$
B) $\sin \theta \frac { \partial u } { \partial r } - \cos \theta \frac { \partial u } { \partial \theta } / r$
C) $\cos \theta \frac { \partial u } { \partial r } - \sin \theta \frac { \partial u } { \partial \theta } / r$
D) $\cos \theta \frac { \partial u } { \partial r } + \cos \theta \frac { \partial u } { \partial \theta } / r$
E) $\sin \theta \frac { \partial u } { \partial r } + \cos \theta \frac { \partial u } { \partial \theta }$