Please thanks!

(1 point) The divergence of a magnetic vector field B must be zero everywhere. Which of the following vector fields cannot be a magnetic vector field? (a) B(x, y, z) = (y2 + z2)i+ (x2 + y2)j - (x2 + 2yz)k ? a magnetic vector field. (b) B(x, y, z) = -xi + yj - zk ? a magnetic vector field. (c) B(x, y, z) = (2xy - x2 +y )it (y -y?)j ? v a magnetic vector field. (d) B(x, y, z) = (xy - xy?)i + (xy - x2y)j ? a magnetic vector field