Energy may exist in different forms such as potential energy when a body is at rest, kinetic energy when the body is in motion, etc.
Energy can neither be created nor destroyed, however, it can be transformed from one form to another. For example, chemical energy may be transformed into mechanical energy or other forms of energy.
D because Carbon and Oxygen form covalent compounds. I wasn't the greatest at chem., but I'm pretty sure this is correct :D let me know if I gave you the right answer.
