The component considered a protein is (a) Body builder. Proteins serve as the primary building blocks for tissues, including muscle tissue. They provide structural support and contribute to muscle growth, repair, and maintenance, making them indispensable for individuals, such as bodybuilders, aiming to increase muscle mass and strength.

Proteins also serve various other functions beyond tissue building, including energy production (b), regulatory roles (c), and serving as enzymes, hormones, and antibodies. However, their role as bodybuilders primarily emphasizes their function in tissue formation and repair.

While energy producers (b), regulatory molecules (c), and bulk enhancers (d) are essential for various physiological processes within the body, they are not classified as proteins. Instead, they may include carbohydrates, fats, vitamins, minerals, and other molecules that serve specific roles in energy metabolism, regulation, and overall health.