Final answer:
The potential energy of the 5-kilogram mass when it is 2 meters above the ground is 98 J.
Step-by-step explanation:
To calculate the potential energy of a mass, you can use the formula PE = mgh, where m is the mass, g is the acceleration due to gravity (approximately 9.8 m/s^2 on Earth), and h is the height above the reference point.
In this case, the mass is 5 kg and the height is 2 meters. So, the potential energy is PE = 5 kg * 9.8 m/s^2 * 2 m = 98 J.
Therefore, the correct answer is C) 20 J.