The primary source of energy for all mammals is a simple sugar.

Glucose is a simple sugar which is essential for the body to gain and store energy. Monosaccharides are broken down component of carbohydrates which cannot be broken down or hydrolyzed further as they are the littlest form of carbohydrates. They are important energy source of the body and through ingestion, they can be directly taken in by the body. As a result, they immediately go to the blood and provide instant energy. They are building blocks of disaccharides and polysaccharides. Types of monosaccharides include glucose, fructose and galactose.  

The answer is c : ) hope this answered your question!