Match the functions f(x, y, z) with the description of their gradients. no reasons needed. (a) x2 + y2 + z2 points radially outward from the z-axis points radially inward toward the z-axis points radially outward from the origin points radially inward toward the origin (b) x2 + y2 points radially outward from the z-axis points radially inward toward the z-axis points radially outward from the origin points radially inward toward the origin (c) 7 x2 + y2 + z2 points radially outward from the z-axis points radially inward toward the z-axis points radially outward from the origin points radially inward toward the origin (d) 7 x2 + y2 points radially outward from the z-axis points radially inward toward the z-axis points radially outward from the origin points radially inward toward the origin