Final answer:
Alexander Hamilton used the Necessary and Proper Clause to justify the establishment of the Bank of the United States.
Step-by-step explanation:
Alexander Hamilton used the Necessary and Proper Clause to justify (a) The establishment of the Bank of the United States. Hamilton believed that the creation of a national bank was necessary and appropriate to fulfill the government's enumerated powers, such as regulating commerce and collecting taxes. His arguments, along with the support of his fellow supporters in Congress, convinced President Washington to sign the legislation creating the bank.