The name given to the US-led coalition invasion of Afghanistan in 2001 was "Operation Enduring Freedom."

Over 80% the worlds 1 billion+ Muslims belong to the Sunni tradition. Around 10-15% belong to the Shia tradition. The two factions originally split over who should rightly succeed the prophet Muhammad upon his death as the leader of the Muslim community. Those who would come to be known as Sunnis backed the eventual successor Abu Bakr, and those who would come to be known as Shiites backed Muhammad's son-in-law, Ali, who would also come to power before being assassinated. The term "Shia" is derived from the term for "party of Ali" in Arabic. From this political split, Sunni and Shia Islam diverged in a number of ways in their respective practices of Islam. This division has historically been a tremendous source of strife between the two groups. Iraq is physically located on the border between the Arab-speaking, Sunni-professing region of the Middle East and the historical center of Shia belief in Persian speaking Iran. As a result, Iraq is a majority Shia country, but the country holds a very large Sunni minority and is subject to foreign influence from its many Sunni neighbors. The Sunni/Shia split is a major determinant of Iraqi politics. 

Of these answer choices the Iranian Revolution only led "directly" to the Oil Crisis of 1979. The Oil Crisis of 1973 was a result of various members of OPEC announcing an oil embargo. The Crisis of 1979 occurred as a result of changes in Iran’s openness to western economic intervention and the conflict that broke out between Iraq and Iran, which led both countries to limit supply of oil. The crisis led to a recession in the United States in 1979 and 1980 and propelled the Soviet Union into the position of the number one oil supplier in the world.

The Iranian Hostage Crisis of 1979 took place, of course, in Iran. It involved the kidnap of just over 50 American diplomats and citizens. The hostage situation lasted for 444 days before the American hostages were finally released. It is seen as one of the seminal moments in the beginnings of American involvement in the Middle East, as well as a notable incident of Carter’s presidency.

The Watergate Scandal occurred in the early 1970s, following a break-in at the Democratic Party headquarters in 1972. It brought about the end of Richard Nixon’s Presidency, after it was revealed that Nixon and his advisors had violated several codes of conduct. This resulted in Nixon’s attempted impeachment and subsequent resignation. It represents an important turning point in American history when, according to many historians, the American public permanently lost faith in the honesty and efficacy of it’s political leaders.