Final answer:
The correct statement about gravitational potential energy is (a) 'When mass falls, it will lose gravitational potential energy.' This occurs because as an object falls, the potential energy is transformed into kinetic energy and other forms.
Step-by-step explanation:
The correct statement about gravitational potential energy is that when mass falls, it will lose gravitational potential energy. This means that as an object descends, the gravitational potential energy it possessed at a higher position is converted to other forms of energy, most commonly kinetic energy. It is important to note that gravitational potential energy depends only on the vertical position relative to a reference point, typically the ground. Lifting an object increases its gravitational potential energy, and this stored energy is the product of its weight (the force due to gravity) and the height it is lifted.
Based on this understanding, we can conclude that statement (a) 'When mass falls, it will lose gravitational potential energy' is the correct one. The other options are incorrect because lifting mass up increases its gravitational potential energy, and travelling horizontally does not affect gravitational potential energy as there is no change in height.