球面x2 + y2 + z2 = 9与平面x + z = 1的交线在xoy坐标面上投影的方程是:

球面x2 + y2 + z2 = 9与平面x + z = 1的交线在xoy坐标面上投影的方程是:

(A) x2 + y2 + (1－x)2 = 9

(C) (1－z)2 + y2 + z2 = 9