Answer: (b) move forward
On applying brakes water tanker comes to rest but water will be in motion this makes the water to come forward.
When a tanker is filled to 2/3 capacity of water, the water inside the tanker moves at the same velocity as the tanker. As a result, it remains constant. When the tanker’s brakes are applied, the tanker’s velocity decreases, but no external force is operating directly on the water. As a result, the tanker’s velocity reduces but the velocity of the water within stays unchanged.