What challenges do metropolitan areas face today and how are these challenges being addressed?

the answer is use of support  

the outcome of 1970 oil crisis in united states was that, they began to search ways on how to reduce oil.

in 1970 was a period when there were energy and oil crisis. those who were major centers for industrialization were forced to keep way from supplying of petroleum.

some of the result of this crisis was economic growth became stagnant because prices of oil surged.

due to the increased prices some countries like mexico and norway benefited.

the correct answer is a