Explanation: GPS satellites orbit in Medium Earth Orbit (MEO) at a precise altitude of approximately 20,200 kilometers, which translates to about 12,554 miles. This specific MEO altitude (option C) is a critical design choice for the GPS system. MEO provides a balance between global coverage with a manageable number of satellites and reasonable signal propagation delays. Each GPS satellite broadcasts precise timing signals via radio waves. Receivers on Earth measure the time difference of arrival from multiple satellites to calculate their position. The known, stable orbital altitude is fundamental to these trilateration calculations. Option D (247 miles) represents a Low Earth Orbit (LEO), which is too low for the GPS constellation to provide global coverage with its current number of satellites. Options A (4,686 miles) is too low for the standard GPS orbit within MEO, while option B (24,184 miles) is close to Geostationary Earth Orbit (GEO), where satellites appear stationary relative to the ground. GPS satellites are not geostationary; they continuously move across the sky as observed from Earth, which is essential for accurate positioning.