Why does an enzyme function as a catalyst in a reaction?

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.

How does secondary succession differ from primary succession?

How do the sperm cells get from the stigma to the ovules?