What system provides defense against close-in, sea-skimming cruise missiles?

The Phalanx system is designed specifically to provide defense against close-in threats, including sea-skimming cruise missiles. It utilizes a radar-guided gun system with a high rate of fire, allowing it to engage targets at short ranges effectively. The Phalanx relies on its ability to quickly track and engage fast-moving threats, which is critical in the defense against missiles that fly at low altitudes to avoid detection by radar.

In contrast, the other options serve different purposes or are designed for different types of engagement. The Tomahawk is a long-range cruise missile primarily used for striking land targets rather than defending against incoming missiles. The Phoenix missile was designed for air-to-air combat in naval aviation, not for close-in missile defense. The Harpoon is an anti-ship missile, also not intended for defending against incoming missiles. Therefore, the Phalanx stands out as the appropriate system for close-in missile defense, given its specific function and capabilities.