Which macromolecule is the primary energy source for organisms?
question 2 options:
a) sunlight
b) protein
c) fat
d) carbohydrate
e) nucleic acid

The correct option is D.
Carbohydrate is the main energy source for living organism. When carbohydrate food are consumed, the digestive enzymes break the carbohydrate down to glucose. The body cells use glucose as a source of fuel to produce energy which they use for their metabolic activities.

Photosynthesis is not taking place and carbon dioxide is not being processed.

Explanation:

The process by which plants make glucose (carbohydrates = energy stores) from carbon dioxide and water is called photosynthesis and uses sunlight energy. A by-product of photosynthesis is oxygen.So plants use water and sunlight to grow and they produce oxygen. Animals on the other hand eat plants, use oxygen and breathe out carbon dioxide.

Since the space station is in the shadow of the earth, the plants are unable to complete the process of photosynthesis and the carbon dioxide that is being produced by the humans cannot be utilized by the plants due to no sunlight. There for the carbon dioxide is going to continue to build up as the energy storage molecules are being depleted and not replenished.