I believe the correct answer from the choices listed above is the third option. It is oxygen that is a necessary reactant for cellular respiration to occur. Cellular respiration, in a sense, is breaking down sugar in the presence of oxygen. Hope this answers the question.
Black stuff from volcanos!
All plants have chlorophyll-a which blocks(reflects) green light and absorbs red and blue wavelengths. It seems like it would be more efficient for plants to absorb green light since energy is most powerful from the sun through green wavelengths. However, the chlorophyll-a in chloroplasts actually defend the plant from harmful damage of the TREMENDOUS amount of power from the sun transmitted in green wavelengths.
SO CHLOROPHYLL-A PROTECTS PLANTS FROM TOO MUCH ENERGY IN GREEN LIGHT.
