What is significant about the Supreme Court’s decision in McCulloch v. Maryland? It was the first time the Supreme Court ruled on the meaning of the “commerce clause.”
It was the first time the Supreme Court ruled in favor of Congress against state laws.
It was the first time the Supreme Court struck down a state law as unconstitutional.
It was the first time the Supreme Court recognized an implied power of Congress.

It was the first time the Supreme Court ruled on the meaning of the “commerce clause.”

Explanation:

the Supreme Court held that Congress has implied powers derived from those listed in Article I, Section 8. The “Necessary and Proper” Clause gave Congress the power to establish a national bank.

four sitting presidents have been assassinated while in office but the first was abraham lincoln,

the anwser is a) to prevent military conflict