Final answer:
Oxygen is the most soluble gas among O2, CO2, and N2 in water due to its paramagnetic and polarizable nature.
Step-by-step explanation:
Oxygen (O2) is considered to be the most soluble gas among O2, CO2, and N2 in water. According to the information provided, O2 is twice as soluble in water as N2. This difference in solubility can be attributed to the fact that O2 is paramagnetic and more polarizable than N2, making it more soluble.