Perform the Indicated Operation $\sqrt { 7 } ( \sqrt { 5 } - \sqrt { 3 } )$

Multiple Choice

Perform the indicated operation. Assume that all variables represent positive real numbers.
- $\sqrt { 7 } ( \sqrt { 5 } - \sqrt { 3 } )$

A) $\sqrt { 35 } - \sqrt { 21 }$
B) $7 \sqrt { 5 } + 7 \sqrt { 3 }$
C) $\sqrt { 56 }$
D) $8 \sqrt { 7 }$