Final answer:
The proportions of gas, liquid, and solid in an underground oil reservoir depend on the geological conditions and the temperature of the reservoir.
Step-by-step explanation:
The proportions of gas, liquid, and solid in an underground oil reservoir depend on several factors, including the geological conditions and the temperature of the reservoir. The geological conditions determine the type of rocks and sediments present, which can affect the formation and migration of oil in the reservoir. The temperature of the reservoir plays a role in the phase behavior of the hydrocarbons, influencing whether they exist as gas, liquid, or solid.