Factor the Expression Completely $$4 z ^ { 2 } + 28 z + 49$$

Factor the expression completely. $$4 z ^ { 2 } + 28 z + 49$$

A) $\quad ( 2 z + 7 ) ^ { 2 }$
B) $\quad 7 ( 2 z + 7 )$
C) $\quad ( 2 z + 7 ) ( 2 z - 7 )$
D) $\quad ( 2 z - 7 ) ^ { 2 }$