The correct answer is (d). The United States has become the largest oil producing nation as per latest data released in July, 2014.
The United States has been increasing its oil production in recent years due to the development of new technologies, such as hydraulic fracturing (fracking). Fracking is a process that allows oil and gas to be extracted from shale rock formations. The United States is now the world’s largest producer of shale oil.
Saudi Arabia is the world’s second-largest oil producer. The country has a long history of oil production and is a member of the Organization of the Petroleum Exporting Countries (OPEC). OPEC is a cartel of oil-producing countries that sets production quotas in an effort to control the global oil market.
Russia is the world’s third-largest oil producer. The country has a large oil industry and is a major exporter of oil. Russia is not a member of OPEC.
Iran is the world’s fourth-largest oil producer. The country has a large oil industry and is a major exporter of oil. Iran is a member of OPEC.
The United States, Saudi Arabia, Russia, and Iran are the world’s four largest oil producers. The United States has become the largest oil producing nation as per latest data released in July, 2014.