Concept:A rising bubble expands because the external pressure on it decreases.
Explanation:Inside the beaker, the bubble is acted upon by atmospheric pressure plus water pressure due to the depth.
As the bubble rises, the depth decreases, so the water pressure on the bubble decreases.
Boyle’s law states that for a fixed amount of gas at constant temperature, pressure is inversely proportional to volume:
P∝V1Therefore, when the pressure on the bubble reduces, its volume increases.
This is why the bubbles get bigger in size as they rise.
Answer:A. water pressure on the bubbles decreases
