Identify the surface whose equation is given. 7r2 + z2 = 1 a sphere centered at the origin with intercepts x = ±1, y = ±1, z = ±1 an ellipsoid centered at the origin with intercepts x = ± 1 7 , y = ± 1 7 , z = ±1 an ellipsoid centered at the origin with intercepts x = ± 1 7 , y = ± 1 7 , z = ±1 a cylinder centered at the origin with intercepts x = ± 1 7 , y = ± 1 7 , z = ±1 a cylinder centered at the origin with intercepts x = ± 1 7 , y = ± 1 7 , z = ±1