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

• A. It produces electrical impulses for muscle contraction.
• B. It acts as the main site of gas exchange with the environment.
• C. It serves as a delivery system, transporting oxygen, nutrients, and waste products.
• D. It stores energy in the form of glycogen.

Answer: (C)

Verified step by step guidance

1. Understand the role of blood in the human body: Blood is a connective tissue that plays a critical role in maintaining homeostasis by transporting essential substances throughout the body.
2. Eliminate incorrect options: Blood does not produce electrical impulses for muscle contraction; this is the role of the nervous system. Similarly, blood is not the main site of gas exchange; this occurs in the lungs (alveoli). Blood also does not store energy in the form of glycogen; glycogen is stored in the liver and muscles.
3. Focus on the correct function: Blood serves as a delivery system, transporting oxygen from the lungs to tissues, nutrients from the digestive system to cells, and waste products like carbon dioxide and urea to excretory organs for removal.
4. Relate to the circulatory system: Blood circulates through the body via the cardiovascular system, which includes the heart, arteries, veins, and capillaries, ensuring efficient transport of substances.
5. Conclude with the correct answer: The primary function of blood is to serve as a delivery system, transporting oxygen, nutrients, and waste products, which aligns with the correct answer provided in the question.