Which operation was launched by the US after 9/11 attack?

Operation Enduring freedom

The correct answer is option (2) - Operation Enduring freedom

The US response to 9/11 attack against Al-Qaeda and the Taliban, 'Operation Enduring Freedom."
Operation Enduring Freedom was the official name used by the U.S. government for the War in Afghanistan, together with three smaller military actions, under the umbrella of the Global War on Terror, and was initiated by President George W. Bush after the September 11 attacks in 2001. As a part of its ‘Global War on Terror’, the US launched ‘Operation Enduring Freedom’ against all those suspected to be behind this attack, mainly Al-Qaeda and the Taliban regime in Afghanistan. The Taliban regime was easily overthrown, but remnants of the Taliban and Al Qaeda have remained potent, as is clear from the number of terrorist attacks launched by them against Western targets since.