<h2>Osmosis.</h2>
Explanation:
The correct order of balloon volumes at equilibrium, from largest to smallest:
Balloon D > Balloon C > Balloon B > Balloon A.
Osmosis is defined as the process of movement of water molecules from the region of their higher concentration to the region of their lower concentration i.e. from a less concentrated concentrated solution to a solution with greater concentration through a semipermeable membrane.
So , In case of balloon A and B water will move out of them and at equilibrium it will have reduced volumes. However, A will lose more water that B.
In case of Balloon C no water movement will be observed it will remain constant.
In case of Balloon D, Water will move inside the balloon and its volume will increase.
Thus at equilibrium the order of balloon volumes will be :
Balloon D > Balloon C > Balloon B > Balloon A.