Answer: The use of oil and coal will end at the same time.
Explanation: A proposal is a plan or road map to achieving a target goal.
Scientists over time have been researching ways of replacing fossil fuels with green energy which is cleaner and more economic friendly.
Therefore there is an ongoing plan to end the use of fossil fuels such as : oils, coal, gas, petrol etc to much cleaner forms of energy like solar energy, wind energy, hydropowered energy.