Find Parametric Equations for the Cylinder $y ^ { 2 } + z ^ { 2 } = 49$

Multiple Choice

Find parametric equations for the cylinder $y ^ { 2 } + z ^ { 2 } = 49$

A) $\vec { r } ( s , \theta ) = 7 \cos \overrightarrow { \theta i } + 7 \sin \theta \vec { j }$
B) $\vec { r } ( s , \theta ) = 7 \cos \theta \vec { i } + 7 \sin \theta \vec { j } + s \vec { k }$
C) $\vec { r } ( s , \theta ) = s \vec { i } + 49 \cos \theta \vec { j } + 49 \sin \theta \vec { k }$
D) $\vec { r } ( s , \theta ) = \operatorname { si } + 7 \cos \theta \vec { j } + 7 \sin \theta \vec { k }$
E) $\vec { r } ( s , \theta ) = \operatorname { si } + 7 \cos \theta \vec { j } + 7 \cos \theta \vec { k }$