B. When electrons gain energy, they have the power to move up to a higher energy level in an atom.
The answer is C, a catalyst. This is due to the fact that catalysts are substances that can be used to speed up a reaction by lowering the activation energy required. However, the catalyst itself is not actually used up during the reaction.
Law of multiple proportions, statement that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.
