Answer: Option (C) is the correct answer.
Explanation:
When we heat a fluid then the movement within the fluid makes hot (less dense) material to rise and cooler (more denser) material to sink at the bottom. This process is known as convection.
Thus, in the diagram hot (less dense) water will rise and cooler (more dense) water sinks at the bottom.
Therefore, we can conclude that according to the arrow the label belongs to cooler water sinks.
