Simplify $\sqrt { x ^ { 2 } - 14 x + 49 }$

Multiple Choice

Simplify $\sqrt { x ^ { 2 } - 14 x + 49 }$ . Assume all variables are unrestricted and use absolute value symbols when necessary.

A) x-7
B) $( x - 7 ) ^ { 2 }$
C) 7|x|
D) | x-7|