Solve for the Specified Variable $\mathrm { M } = \pi \mathrm { r } ^ { 2 } \mathrm { hd }$

Multiple Choice

Solve for the specified variable. Assume that all other variables are nonzero
- $\mathrm { M } = \pi \mathrm { r } ^ { 2 } \mathrm { hd }$ ; for $\mathrm { r }$

A) $\mathrm { r } = \frac { \pm \sqrt { \mathrm { M } \pi h d } } { \pi \mathrm { hd } }$
B) $r = \frac { \pm \sqrt { \pi \mathrm { Mhd } } } { \text { hd } }$
C) $r = \frac { \pm M \sqrt { \pi h d } } { \pi h d }$
D) $r = \pm \sqrt { \pi M h d }$