What is the function of the immune system?

Correct Answer: B

Rationale: The correct answer is B: 'To fight infection.' The immune system's primary function is to protect the body from infections and foreign invaders by recognizing and responding to pathogens. It plays a crucial role in maintaining overall health and preventing diseases caused by harmful microorganisms. Choices A, C, and D are incorrect because the immune system is not responsible for transporting oxygen, digesting food, or producing hormones. These functions are carried out by other systems in the body, such as the respiratory system, digestive system, and endocrine system, respectively.

Correct Answer: A

Rationale: The rib cage is the correct answer. It plays a crucial role in protecting vital organs like the lungs and heart. The rib cage forms a protective barrier around these organs, shielding them from external trauma or injuries. It acts as a sturdy cage, offering structural support and safeguarding the delicate tissues and structures of the lungs and heart. The pelvis, femur, and vertebral column do not directly protect the lungs and heart; instead, they have other important functions in the body, such as supporting the body's weight, enabling movement, and protecting the spinal cord.

Correct Answer: B

Rationale: The correct answer is B: Mitochondria. Mitochondria are known as the powerhouse of the cell and are responsible for producing energy in the form of ATP through the process of cellular respiration. The other organelles listed, such as the nucleus, Golgi apparatus, and ribosome, have different functions within the cell and are not directly involved in energy production. The nucleus is responsible for storing genetic material and controlling cell activities. The Golgi apparatus is involved in modifying, sorting, and packaging proteins. Ribosomes are responsible for protein synthesis.

Correct Answer: B

Rationale: The small intestine is the primary site where the absorption of nutrients from digested food occurs. Its large surface area, specialized cells, and villi play key roles in maximizing nutrient absorption, making it the structure in the digestive system that absorbs the most nutrients. The stomach's main function is to break down food with acid and enzymes, not absorb nutrients. The large intestine primarily absorbs water and electrolytes, not nutrients. The esophagus is a muscular tube that connects the throat with the stomach and does not play a role in nutrient absorption.

Correct Answer: B

Rationale: The correct answer is B: Thyroid gland. The thyroid gland is responsible for regulating the body's metabolism by producing hormones like thyroxine. These hormones play a key role in controlling the body's metabolic rate and energy production. Choice A, the pituitary gland, is often referred to as the 'master gland' but is not primarily responsible for regulating metabolism. Choice C, the adrenal gland, is involved in producing hormones like adrenaline and cortisol, which are crucial for the body's stress response but not primarily for metabolism. Choice D, the pineal gland, is responsible for producing melatonin, which regulates sleep-wake cycles and not directly related to metabolic regulation.