What is another metaphor (aside from the fact that a piano can only produce certain notes) that could help someone understand energy quantization at the atomic level?

The correct answer is  "c".  it is "c" because melting is an endothermic change, and endothermic get's energy from surroundings. 

The best answer is (a) which is universal law is in effect at all times. it is constantly at play in everything we do and governs our lives. it is also important to note that universal law applies to not only everything on earth, but everything in the universe as well, which is another reason why it is in effect at all times.

Ibelieve that the correct answer is: c. along plate boundaries

All u need to do is see how 50cm work with each other