A solid cuboid is held fully submerged in a tank of water. Which of the following best explains why the water exerts a net upward force on the cuboid?
(a) Atmospheric pressure acts only on the upper surface, producing an upward thrust.
(b) The water's density is greater than that of the cuboid, so the denser fluid automatically pushes the cuboid upward.
(c) Pressure on the bottom face is greater than on the top face because pressure increases with depth.
(d) Water molecules strike the cuboid from all directions with equal momentum change, so there should be no net force.