D

After the end of the Cold War，the United States became the sole super power in the world.However，the end of the Cold War did not bring peace and harmony to the world or the United States，as the U.S.took on an international policing role.To protect its overseas interests and value system，the U.S.government kept the military budget high and carried out military actions in foreign countries.

The most troublesome region for the United States was the Middle East，from which it imported large quantities of oil.In 1973，when the oil exporting countries in the Middle East imposed an oil embargo on the United States because of its pro⁃Israel policies，America suffered an economic recession.In 1979，Iran took more than 50 Americans hostage who were not released until early 1981 after the United States agreed to unfreeze some Iranian assets in America.In 1990，the United States fought the Gulf War to reverse Iraq’s invasion of Kuwait.Although the U.S.won the war，President George H.W.Bush lost the presidential election to Bill Clinton in 1992 because of the poor performance of the economy at home.

Bill Clinton was elected President as a“New Democrat”.He did not believe in big government and made great efforts to cut government spending and to promote free trade.In his first term，Clinton pushed through Congress two major trade agreements：the North American Free Trade Agreement（NAFTA）in 1993 and the treaty that created the World Trade Organization in 1994.In 1999，Clinton signed a trade agreement with China which granted China permanent“normal trade relations”status and supported China’s candidacy to join the World Trade Organization.This accord promoted trade between the two countries significantly.During Clinton’s administration，the United States experienced the longest period of economic growth in its history.

Clinton also succeeded in implementing some social reforms.He reformed the welfare system and signed the welfare⁃to⁃work bill which encouraged welfare recipients to find jobs.The law limited welfare benefits to five years and required adults to work after the first two years in order to remain on the welfare rolls.He signed the Family and Medical Leave Act which provided that businesses employing more than 50 people had to allow staff up to 12 weeks of unpaid leave to take care of family matters.He expanded tax credits for low⁃income families，and he was also the first President to support equal rights for homosexuals and supported women’s right to have abortions.

Although Clinton achieved a great deal in his presidency，he was enmeshed in scandals and became only the second President to be impeached by Congress.Beginning in the first year of his presidency，he was investigated by an independent prosecutor for his investment in the Whitewater Development Corporation，a real estate company.Although the independent prosecutor never found evidence of wrongdoing with regard to the Whitewater investment，he did find that Clinton had become sexually involved with a young White House intern.In December 1998，Clinton was impeached by the House of Representatives for lying to a Grand Jury about the matter and for obstructing justice.However，the Republicans in the Senate did not secure enough votes to remove him from office.Clinton was able to move beyond the impeachment and completed his second term with a high public approval rating.

Clinton was succeeded in 2001 by George W.Bush of the Republican Party，son of former President George H.W.Bush，after a very close presidential election in 2000.Bush’s administration experienced many problems.Shortly after he took office，the economy began to slow down.Increase in GNP fell to around 2％ and many businesses went bankrupt.Unemployment rate went high and people’s saving rate dropped to historical low.

Terrorists Destroyed the World Trade Center on September 11，2001

The most serious problem Bush faced was terrorism.U.S.policies in the Middle East caused great resentment in the Muslim world，and Islamic extremists had previously launched terrorist attacks against the United States.However，the most serious terrorist attack happened on September 11，2001 when terrorists hijacked four passenger planes in the United States and used them as missiles against predetermined targets.Two of the planes flew into the twin towers of the World Trade Center in New York City and caused them both to collapse，killing more than 2，800 people.Another plane flew into the Pentagon outside of Washington D.C.and killed 125 people.Passengers on the fourth hijacked plane realized what was going on and fought the hijackers，which caused the plane to crash in Pennsylvania.

The September 11 attacks were an enormous shock to the United States.In response，the Bush administration launched a war against Afghanistan early October 2001 after the Afghan government refused to expel the Islamic extremist leader Osama Bin Laden.The Bush administration subsequently focused its attention on Iraq，accusing the Iraqi government of developing weapons of mass destruction and supporting terrorism.The United States invaded Iraq in 2003 without the approval of the United Nations.Many countries opposed the war，including traditional U.S.allies such as France，Germany and Canada.

The American⁃led forces quickly overthrew the Iraqi government and occupied the entire country，but they failed to maintain peace in Iraq.More American troops had sent to Iraq after President Bush declared in May 2003 that the mission had been accomplished.By February 2007，the total number of occupying troops in Iraq reached more than 150，000.In addition，the failure to find weapons of mass destruction in Iraq as well as a lack of evidence of Iraq’s involvement in the September 11 attacks led to a loss of credibility for the Bush administration.As a result，the Republican Party lost control over Congress in the midterm elections of 2006 as the Democratic Party won more seats than the Republicans in both houses.In 2008，the Democratic Party regained the White House when Barack Obama became the first African American to become U.S.president.