Which of the following ranks is the highest?

Petty Officer First Class is the highest rank among the choices listed. In the U.S. Navy's rank structure, Petty Officer First Class is classified as an E-6 rank, representing a veteran and experienced non-commissioned officer who has taken on significant responsibilities. This rank is above Petty Officer Third Class, which is an E-4, and encompasses a greater level of expertise, leadership abilities, and duties.

The other ranks listed, including Seaman and Seaman Apprentice, are significantly lower in the hierarchy. Seaman, ranked as E-3, and Seaman Apprentice, ranked as E-2, are considered entry-level positions within the Navy. These ranks are typically associated with training and early stages in a sailor’s career, focusing on gaining foundational skills and experience. Thus, Petty Officer First Class is the most advanced and indicates a higher level of accomplishment and standing within the Navy's structured ranks.