What act established the United States Marine Corps?

The Continental Marine Act of 1775 is the correct answer because it specifically authorized the creation of two battalions of Marines to serve during the American Revolutionary War. This act established the Marine Corps as a distinct military force separate from the Navy and the Army, focusing on shipboard duties and enabling land engagements as needed. The founding of the Marine Corps on November 10, 1775, is commemorated every year as the Corps' birthday, marking its inception as an essential branch of the United States military.

The other acts mentioned do not relate specifically to the formation of the Marine Corps. The Naval Appropriation Act of 1750 focused on funding naval operations, the Marine Corps Reorganization Act of 1792 dealt with reorganizing the already established Marine Corps, and the Military Act of 1789 primarily dealt with the overall organization of the military forces of the United States, but did not specifically create the Marine Corps.