Q: Which method would increase the solubility of a gas?

Flexi Says:

Pressure has very little effect on the solubility of solids or liquids, but has a significant effect on the solubility of gases. Gas solubility increases as the partial pressure of a gas above the liquid increases. Suppose a certain volume of water is in a closed container with the space above it occupied by carbon dioxide gas at standard pressure. Some of the CO₂ molecules come into contact with the surface of the water and dissolve into the liquid. Now suppose that more CO₂ is added to the space above the container, causing a pressure increase. More CO₂ molecules are now in contact with the water and so more of them dissolve. Thus the solubility increases as the pressure increases. As with a solid, the CO₂ that is undissolved reaches an equilibrium with the dissolved CO₂, represented by the following equation.