Factor the Polynomial Completely $7 x ^ { 2 } - 21 x z - 28 z ^ { 2 }$

Multiple Choice

Factor the polynomial completely.
- $7 x ^ { 2 } - 21 x z - 28 z ^ { 2 }$

A) $7 ( x - z ) ( x + 4 z )$
B) $7 ( x + z ) ( x - 4 z )$
C) $( 7 x - 7 z ) ( x + 4 z )$
D) prime polynomial