Why Is Organization of Petroleum Exporting Countries (OPEC) So Important

Why is Organization of Petroleum Exporting Countries (OPEC) so important?

A) Together, the member countries have about 81% of the world's proven crude oil reserves, giving them significant ability to control world oil supplies for the foreseeable future.
B) It consists of three countries with about half of the world's proven crude oil reserves.
C) Together, the member countries are the major players in international policy regarding the implementation of progressive and unconventional resources.
D) The member countries control the largest reserves of unconventional resources, including tar sands and shale gas.
E) The member countries consume the largest amount of petroleum products in the world and therefore have a significant effect upon petroleum prices.