Find the Center and Radius of the Sphere $x ^ { 2 } + y ^ { 2 } + z ^ { 2 } - 14 z = 0$

Multiple Choice

Find the center and radius of the sphere. $x ^ { 2 } + y ^ { 2 } + z ^ { 2 } - 14 z = 0$

A) center: (0,0,0) ;radius: 49
B) center: (0,0,7) ;radius: 49
C) center: (0,0,-7) ;radius: 7
D) center: (0,0,7) ;radius: 7
E) center: (0,0,0) ;radius: 0