B. He thought it was unconstitutional.
Step-by-step explanation:
Thomas Jefferson was opposed to Hamilton's national bank because he felt that it was unconstitutional and nowhere did the Constitution state that a national bank could be created.
Hamilton believed that a national bank was needed, as he wanted to improve the nation and its economy. As the country was growing and the Constitution was created, he thought it would be beneficial to have a national bank and it was needed for taxation. Hamilton was a "loose constructionist" and he did not follow the Constitution strictly, he thought the Constitution should be up for interpretation and he often would use the elastic clause to push for what he wanted.
Jefferson was a "strict constructionist" and believed that the Constitution should not be up for interpretation and that everything that the Constitution says should be taken as it is and not be stretched out. He was against the national bank, as nowhere in the Constitution does it state that the government has the power to create that. Still, Hamilton used the "necessary and proper" clause that was stated in the Constitution.