The best and most correct answer among the choices provided by the question is the fourth choice which is all of the above.
The use of fossil fuels makes the US vulnerable because it is an exporter of the fuel, and also it imports its petroleum from foreign countries most especially the Middle East. I hope my answer has come to your help. God bless and have a nice day ahead!
Russia has a population of 144 million people (in 2015). Moscow is the capital and core of political power and the center of culture, and trade, St. Petersburg is the second largest city.