Which system's primary responsibility is guiding missiles?

The primary responsibility of guiding missiles falls to the Rolling Airframe Guided Missile (RAM) system. RAM is specifically designed to provide close-in defense against anti-ship missiles and other aerial threats. It utilizes advanced guidance systems that enable it to effectively track and guide projectiles towards targets.

In the context of this question, while the Aegis Combat System provides overall command and control capabilities, including missile guidance through its integrated systems, its primary function is broader, encompassing the coordination of various weapon systems rather than being solely dedicated to guiding missiles. The Mk 45 Gun, primarily used for naval surface fire support, does not guide missiles but fires standard naval projectiles. The Harpoon Missile System, while it does engage targets, relies on its own internally programmed guidance rather than acting as a guiding system like RAM.

Consequently, RAM is distinct in its direct responsibility for missile guidance, making it the correct choice in this scenario.