Let f(x,y)=144-x-y2 (A) Describe the cross sections of the surface z = f(x,y) produced by cutting it with the planes y = 1, y = 4, and y = 7. (B) Describe the cross sections of the surface in the planes x = 1, x = 4, and x = 7. (C) Describe the surface z = f(x,y). (A) Choose the best description of the cross sections in the planes y = 1, y = 4, and y = 7. OA. Upper semicircles whose centers lie on the y-axis. OB. Up opening parabola in the xz-plane. OC. Down opening parabola in the yz-plane. D. Lower semicircles whose centers lie on the x-axis.