Acatalyst is not a product or a chemical reaction. why not

Which of the following is a possible reason for sleep? a) growth b)digestive c)speed d)intelligence

Which of the following is the best definition for the process of photosynthesis? a.) plants digest sugars to make energy. b.) plants use oxygen and glucose to make carbon dioxide. c.) plants use sunlight and carbon dioxide to make sugars. d.) plants use sunlight to make chlorophyll and chloroplasts.

When a gasoline engine burns gasoline, what type of chemical reaction is occurring?