Answer: Option (b) is the correct answer.
Step-by-step explanation:
A process in which a fluid is heated then cold material (more dense) sinks at the bottom whereas hotter material (less dense) rises at the top is known as convection.
In convection, heat transfers from burner to the vessel and further it reaches to the fluid present into the vessel.
Therefore, we can conclude that the given situation represents convection as the kind of transfer of heat.