Final answer:
The mass of a planet can be determined by equating its gravitational and centripetal accelerations with a small satellite. The orbital radius, mass of the satellite, and period of the satellite's orbit are required for this calculation, but the gravitational constant is not needed.
Step-by-step explanation:
The correct answer is c. Gravitational constant. When determining a planet's mass using the gravitational and centripetal acceleration, the orbital radius of the satellite, mass of the satellite, and period of the satellite's orbit are all necessary values. However, the gravitational constant, represented by the symbol G, is not required for this calculation.