Simplify the Radical Expression $\sqrt { 28 x ^ { 2 } }$

Multiple Choice

Simplify the radical expression. The variable represents a positive real number. $\sqrt { 28 x ^ { 2 } }$

A) $2 + x \sqrt { 7 }$
B) $2 + x + \sqrt { 7 }$
C) $2 x \sqrt { 7 }$
D) $7 x \sqrt { 5 }$
E) $2 \sqrt { 7 x }$