Answer: Reservoir pressure declines over time, so different approaches are required to increase the pressure of hydrocarbons in the reservoir and conduct advanced oil recovery, such as the injection of gas into the reservoir, water injection, or the installation of a pump inside the drilled well. Thus, the injection of gas into the reservoir to increase pressure is not the only method of advanced oil recovery, and option A is not correct. Option B is not correct either as it is used for both electricity generation and transportation. Option C is completely correct as natural gas is used as a source of energy for industrial, commercial, and residential areas. Option D is also correct because burning natural gas in a flare system is not an economical or environmentally friendly option. Thus, options C and D are the correct answers.