Which organ is involved in the immune system?

Correct Answer: C

Rationale: The correct answer is the Appendix. The appendix is now known to play a role in the immune system by housing beneficial bacteria that aid in maintaining gut health and supporting immune responses. This organ contributes to overall immune function. Choices A, B, and D are incorrect as the heart, bronchi, and esophagus are not primarily associated with the immune system.

Correct Answer: B

Rationale: The primary function of the respiratory system is to facilitate the exchange of gases. It transports oxygen from the air into the bloodstream, which is crucial for cellular respiration and providing energy to the cells. Additionally, it removes carbon dioxide, which is a waste product that needs to be eliminated. Choices A, C, and D are incorrect because while the respiratory system does remove carbon dioxide, its primary role is oxygen transport, not nutrient delivery, sound, or speech production.

Correct Answer: B

Rationale: The small intestine is the primary site for nutrient absorption in the digestive system. It plays a crucial role in absorbing digested food into the bloodstream, where the nutrients are then circulated to the body's cells for energy and other functions. The stomach primarily breaks down food through the action of acids and enzymes, while the large intestine absorbs water and salts, not nutrients. The esophagus is a muscular tube that connects the mouth to the stomach and does not participate in nutrient absorption.

Correct Answer: B

Rationale: The correct answer is B: Remove carbon dioxide from the body. The primary function of the lymphatic system is to return excess tissue fluid to the bloodstream and assist in the body's defense against infections by filtering out harmful pathogens and foreign particles. Choices A, C, and D are incorrect because transporting oxygen to cells is mainly done by the circulatory system, hormone production is primarily carried out by endocrine glands, and nutrient transport is also a function of the circulatory system and the digestive system, not the lymphatic system.

Correct Answer: A

Rationale: The correct answer is A: Protecting the body from external damage. The primary function of the integumentary system, which includes the skin, hair, and nails, is to act as a physical barrier that protects the body from external damage such as pathogens, UV radiation, and mechanical injuries. While the integumentary system does play roles in regulating body temperature and producing vitamin D, its main and most crucial function is to provide a protective shield for the body. Choices B, C, and D are incorrect because although the integumentary system contributes to regulating body temperature and producing vitamin D, as well as housing cells involved in the immune response, its primary role is protection.