Answer : 3. "high pressure and low temperature"
Explanation :

Answer: C) high pressure and low temperature Explanation: Henry's Law tells that the solubility of a gas is directly proportional to the partial pressure of the gas above the solvent. Hence under high pressure, more gas is dissolved. Also that Henry's Law involves a constant which is temperature-dependent. Under high temperatures, less gas is dissolved whereas under low temperatures, more gas is dissolved.   For Example ::   You can think of a can of soda. The contents are under pressure and if you shake the can before opening, the soda fizzes out all over as you open it. So the higher the pressure, the more gas or more CO2 can be dissolved in the drink. Eliminate choices 1 and 2. Now focus on the temperature. Soda goes flat (loses carbonation or gas) as it warms up. Soda is usually served cold because more of the carbonation or CO2 stays in the drink when the soda is cold.   Hence, in high pressure and low temperature conditions gases are most soluble in water.