In the given question, a statement of Assertion is followed by a statement of Reason. Mark the correct answer.

Assertion: On 11 September 2001, nineteen hijackers hailing from a number of Arab countries took control of four American commercial aircraft shortly after takeoff and flew them into important buildings in the US.
Reason: As a part of its ‘Global War on Terror’, the US launched ‘Operation indefinite strike’ against all those suspected to be behind this attack, mainly Al-Qaeda and the Taliban regime.

The Assertion is correct but the Reason is incorrect.

The US response to 9/11 was swift and ferocious. Clinton had been succeeded in the US presidency by George W. Bush of the Republican Party, son of the earlier President George H. W. Bush. Unlike Clinton, Bush had a much harder view of US interests and of the means by which to advance them. 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.