Which altitude guarantees obstacle clearance and navigational signal coverage between two radio fixes?

The Minimum Enroute Altitude (MEA) is the correct choice as it is specifically designed to provide obstacle clearance and ensure navigational signal coverage along a route between two radio fixes. The MEA guarantees that an aircraft will maintain a safe altitude above terrain and obstacles, while also being within range of the navigational signals received from ground stations.

This altitude is particularly important for effective navigation and safety, ensuring pilots have a reliable reference for altitude during enroute flight phases. Pilots can trust that flying at or above this altitude will provide a buffer from obstacles while ensuring the integrity of their navigational signals, which aids in maintaining the intended flight path.

In contrast, other altitudes like the Minimum Obstruction Clearance Altitude (MOCA) are designed to provide vertical clearance over obstacles but may not guarantee signal coverage for the entire route. The Off Route Obstruction Clearance Altitude (OROCA) serves a similar purpose but is used in more remote areas where MEA may not be established, while the Minimum Crossing Altitude is related to specific crossings at certain waypoints or intersections, lacking the broad applicability of the MEA for overall flight safety and navigation.