Answer: A
Explanation:
Fun fact, Clones dont have any genetic variation
Green plants and trees use photosynthesis to make food from sunlight, carbon dioxide and water in the atmosphere: It is their primary source of energy. The importance of photosynthesis in our life is the oxygen it produces. Without photosynthesis there would be little to no oxygen on the planet.
Explanation:
The answer is D. Krebs cycle. the Krebs cycle only occurs when oxygen is present, and so it would seem to be the same for the electron transport system... although, in anaerobic bacteria, it is still used as a respiratory electron transport chain called physolmere.
Both genes need to be recessive in order for a recessive trait to be expressed.
I hope this helps!