Write the Specified Quantity as a Function of the Specified $V = \pi r ^ { 3 }$

Multiple Choice

Write the specified quantity as a function of the specified variable.
-The height of a right circular cylinder equals its diameter. Write the volume of the cylinder as a function of its radius.

A) $V = \pi r ^ { 3 }$
B) $V = 4 \pi r$
C) $V = 2 \pi r ^ { 3 }$
D) $V = \frac { 1 } { 2 } \pi r ^ { 3 }$