The correct answer is D. Collagen.
Collagen is a protein that is the main structural component of connective tissue. It is found in skin, bones, tendons, ligaments, and cartilage. Collagen is also found in the walls of blood vessels and the digestive system.
Lipids are a type of molecule that includes fats, oils, and waxes. They are found in all cells and are an important source of energy. Lipids are also used to make hormones and other substances that are necessary for the body to function properly.
Carbohydrates are a type of molecule that includes sugars, starches, and cellulose. They are the body’s main source of energy. Carbohydrates are also used to make other substances that are necessary for the body to function properly.
Cholesterol is a type of lipid that is found in the blood. It is an important substance for the body, but too much cholesterol can lead to health problems such as heart disease.
In conclusion, the major constituent of connective tissue is collagen. Collagen is a protein that is found in skin, bones, tendons, ligaments, and cartilage. It is also found in the walls of blood vessels and the digestive system.