What is the rank insignia for an O-1 in the Marine Corps?

In the Marine Corps, the rank insignia for an O-1, which is the rank of Second Lieutenant, is represented by one gold bar. This insignia visually signifies the officer's entry-level position in the officer rank structure. Second Lieutenants often serve as the first level of leadership and management, where they begin to learn the responsibilities of being an officer in the Marine Corps.

The other options represent different ranks: one silver bar is associated with First Lieutenant (O-2), two attached silver bars denote Captain (O-3), and one gold oak leaf symbolizes Major (O-4). Understanding these insignias helps in identifying the rank and corresponding level of authority within the Marine Corps hierarchy.