How would a drop in the price of oil be expected to affect the excavation of oil sands? What are two benefits of using natural gas? What are two concerns? What are two advantages and two disadvantages...

How would a drop in the price of oil be expected to affect the excavation of oil sands? What are two benefits of using natural gas? What are two concerns? What are two advantages and two disadvantages of using coal as a source of energy? Why are supply-side policies aimed at reducing U.S. dependence on foreign oil usually considered to be environmentally unsustainable?