Write a Chain Rule Formula for the Following Derivative $\frac { \partial \mathrm { u } } { \partial \mathrm { x } }$

Multiple Choice

Write a chain rule formula for the following derivative.
- $\frac { \partial \mathrm { u } } { \partial \mathrm { x } }$ for $\mathrm { u } = \mathrm { f } ( \mathrm { r } , \mathrm { s } , \mathrm { t } ) ; \mathrm { r } = \mathrm { g } ( \mathrm { y } ) , \mathrm { s } = \mathrm { h } ( \mathrm { z } ) , \mathrm { t } = \mathrm { k } ( \mathrm { x } , \mathrm { z } )$

A) $\frac { \partial \mathrm { u } } { \partial \mathrm { x } } = 0$
B) $\frac { \partial \mathrm { u } } { \partial \mathrm { x } } = \frac { \partial \mathrm { u } } { \partial \mathrm { t } }$
C) $\frac { \partial u } { \partial x } = \frac { \partial t } { \partial x }$
D) $\frac { \partial \mathrm { u } } { \partial \mathrm { x } } = \frac { \partial \mathrm { u } } { \partial \mathrm { t } } \frac { \partial \mathrm { t } } { \partial \mathrm { x } }$