If dehydrogenation reactions were not possible and cells could only carry out basic redox reactions, how would this affect the ability of cells to harness energy from the breakdown of carbohydrates?.

the answer is:

carbon dioxide

because the light is a great source of energy for the plants to survive. (i hope this )

igneous rocks which formed by the crystallization of magma at the surface of the earth called extrusive rocks. they are characterized by fine-grained textures because the rapid cooling at or near the surface did not provide enough time for large crystals to grow.