What role do red blood cells play in the body?

Red blood cells, also known as erythrocytes, are essential components of the circulatory system, primarily responsible for transporting oxygen throughout the body. They achieve this through a protein called hemoglobin, which binds to oxygen molecules in the lungs and carries them to tissues and organs. By effectively delivering oxygen, red blood cells play a crucial role in maintaining cellular metabolism and overall energy levels within the body.

The other options reflect functions that are attributed to different cell types or biological processes. For instance, hormone synthesis is predominantly carried out by endocrine glands, while digestion is primarily the responsibility of the gastrointestinal system and its associated enzymes. Additionally, the production of antibodies is a function of B lymphocytes, a type of white blood cell, rather than red blood cells. Thus, the significant role of red blood cells in facilitating oxygen transport makes the correct answer clear in the context of human biology and nutrition.