Answer :
The Bush Doctrine referred to the belief that the United States had the right to defend itself from potential enemies (b) and it was used as an excuse to invade Afghanistan.
The correct answer is option b) "a belief that the Unites States had the right to remove perceived threats". The Bush Doctrine refers to various related foreign policy principles adopted by President George W. Bush, as a result of the 9/11 terrorist attacks. These policies were associated with preventive war under the notion that US had the right to secure itself against countries that harbor or give aid to terrorist groups. This led to US invading Iraq under the premise that it was a perceived threat.