$\text { Find the velocity vector in terms of } u _ { r } \text { and } u _ { \theta } \text {. }$

Multiple Choice

$\text { Find the velocity vector in terms of } u _ { r } \text { and } u _ { \theta } \text {. }$
- $\mathrm { r } = \mathrm { a } ( 2 - \cos \theta )$ and $\frac { \mathrm { d } \theta } { \mathrm { dt } } = 7$

A) $\mathbf { v } = ( 7 a \sin \theta ) \mathbf { u } _ { \mathrm { r } } + 7 \mathrm { a } ( 2 - \cos \theta ) \mathbf { u } _ { \theta }$
B) $\mathbf { v } = ( 7 a \cos \theta ) \mathbf { u } _ { \mathrm { r } } + 7 \mathrm { a } ( 2 - \sin \theta ) \mathbf { u } _ { \theta }$
C) $\mathbf { v } = 7 a ( 2 - \cos \theta ) \mathbf { u } _ { \mathbf { r } } + ( 7 \mathrm { a } \sin \theta ) \mathbf { u } _ { \theta }$
D) $\mathbf { v } = ( 2 a \sin \theta ) \mathbf { u } _ { \mathrm { r } } + 2 \mathrm { a } ( 7 - \cos \theta ) \mathbf { u } _ { \theta }$