Explanation: A RADAR echo travels from the antenna to the target and back, meaning it covers twice the stated distance. For a target 5 miles away, the total travel distance for the pulse is 10 miles. In amateur radio and general radar calculations, "miles" in distance problems are often interpreted as *nautical miles*. A common constant for radar range calculations states that a radio wave travels one nautical mile and returns (a round trip) in approximately 12.36 microseconds. Therefore, for a target 5 nautical miles away, the total time for the echo to be received back at the antenna is $5 \text{ nautical miles} \times 12.36 \text{ microseconds/nautical mile (round trip)} = 61.8 \text{ microseconds}$. This value closely matches option D. Other options do not align with standard radar calculation constants.