The following four vector fields are given in Cartesian

The following four vector fields are given in Cartesian co-ordinate system. The vector field which does not satisfy the property of magnetic flux density is

1. y²a_x + z²a_y + x²a_z
2. z²a_x + x²a_y + a²a_z
3. x²a_x + y²a_y + z²a_z
4. y²z²a_x + x²z²a_y + x²y²a_z

For magnetic fields
∇ . B = 0
Now from options,
(a) ∇ . B = (0) + 0
(b) ∇ . B = 0
(c) ∇ . B = 2x + 2y + 2z ≠ 0
∴ Option (c) is correct