Which of the following best describes the function of red blood cells in the human body?

The primary function of red blood cells in the human body is to carry oxygen from the lungs to the body's tissues and organs. Red blood cells contain a protein called hemoglobin, which binds to oxygen in the lungs and transports it throughout the body via the circulatory system. This oxygen is then released to the tissues, where it is used for various physiological processes, including cellular respiration.

White blood cells, not red blood cells, are primarily responsible for fighting off infections and protecting the body against pathogens. Hormone production is primarily carried out by specialized endocrine glands and cells, not red blood cells. Waste filtration is primarily performed by the kidneys, not red blood cells.