Answer:
The correct option is B.
Explanation:
Carbohydrates are the major macro molecules that are used as a source of fuel in biological systems. The smallest unit of carbohydrate is glucose and this is the only macro molecule that biological systems can use to produce energy. Other macro molecules such as fats and proteins can be converted to glucose if their is shortage of glucose in the body.
Generally, carbohydrates have high level of energy in their reduce electrons, thus, when they are oxidized they give rise to large amount of energy, which can be used to do work in the biological systems.
