What is the primary function of the skin?

Correct Answer: B

Rationale: The primary function of the skin is to protect the body from external damage. While the skin also helps regulate body temperature and produces vitamin D in response to sunlight, its main role is to act as a barrier against harmful external factors, such as pathogens and physical injuries. Choices A, C, and D are incorrect because although the skin does play a role in regulating body temperature and producing vitamin D, its primary function is providing protection against external threats.

Correct Answer: B

Rationale: The central nervous system comprises the brain and spinal cord, responsible for processing and transmitting information. The retina, though part of the eye, is an extension of the central nervous system. However, the heart is part of the circulatory system, responsible for pumping blood throughout the body. Therefore, the correct answer is the heart as it is not a component of the central nervous system.

Correct Answer: A

Rationale: The primary function of the nervous system is to transmit signals and coordinate body activities. It controls and regulates body functions by sending and receiving signals between different parts of the body, enabling responses to internal and external stimuli. This intricate network allows for communication between the brain, spinal cord, and the rest of the body, ultimately facilitating movement, sensation, thoughts, and various bodily functions. Choices B, C, and D are incorrect as they do not represent the primary function of the nervous system. Fighting infections is primarily the role of the immune system, producing hormones is the function of the endocrine system, and regulating body temperature involves mechanisms of thermoregulation within the body, not directly controlled by the nervous system.

Correct Answer: B

Rationale: Vitamin D is the correct answer. It is essential for the absorption of calcium in the intestines, facilitating the maintenance of strong bones and teeth. Vitamin D helps regulate calcium levels in the blood and promotes bone mineralization, making it crucial for overall bone health. Choices A, C, and D are incorrect because Vitamin C is not directly involved in calcium absorption, Vitamin A is more related to vision and immune function, and Vitamin K plays a role in blood clotting and bone mineralization but is not primarily responsible for calcium absorption.

Correct Answer: B

Rationale: The lens of the eye is responsible for focusing light onto the retina. It plays a crucial role in bending light rays to ensure that they converge on the retina, enabling clear vision. The cornea helps in focusing light, but the final adjustment and fine-tuning occur through the lens. The retina receives the focused light and converts it into neural signals for the brain to interpret. The pupil, on the other hand, controls the amount of light entering the eye by dilating or constricting.

Correct Answer: A

Rationale: The correct answer is A: To secrete digestive enzymes. The pancreas is responsible for secreting digestive enzymes that aid in breaking down carbohydrates, fats, and proteins in the small intestine, facilitating the process of digestion. Choice B is incorrect because the pancreas does not store bile; that is primarily the function of the gallbladder. Choice C is incorrect as the absorption of nutrients mainly occurs in the small intestine, not the pancreas. Choice D is incorrect as the transport of glucose is primarily regulated by insulin produced in the pancreas, but this is not the main role of the pancreas in digestion.

Correct Answer: A

Rationale: The correct answer is Vitamin C. Vitamin C is essential for the absorption of iron, especially from plant-based sources. It aids in converting non-heme iron (found in plants) into a form that is easier for the body to absorb. This is crucial in preventing iron-deficiency anemia, making Vitamin C a key nutrient for overall health. Vitamin D (choice B) is important for calcium absorption and bone health, not iron absorption. Vitamin K (choice C) plays a role in blood clotting and bone metabolism, not iron absorption. Vitamin B12 (choice D) is important for red blood cell formation and neurological function but is not directly involved in iron absorption.

Correct Answer: B

Rationale: The correct answer is B: Absorbing nutrients. The small intestine plays a crucial role in digestion by absorbing nutrients. It is where the majority of nutrient absorption occurs, allowing digested food to pass into the bloodstream for distribution to the body's cells. Choice A (Breaking down fats) is incorrect because the breakdown of fats primarily occurs in the small intestine with the help of bile from the liver and enzymes from the pancreas. Choice C (Secreting digestive enzymes) is incorrect because while the small intestine does produce some digestive enzymes, its primary role is absorption. Choice D (Storing bile) is incorrect as the storage of bile occurs in the gallbladder, not the small intestine.

Correct Answer: B

Rationale: The small intestine is the primary site for nutrient absorption in the digestive system. It is responsible for absorbing nutrients from the digested food into the bloodstream for distribution throughout the body. Therefore, the correct function of the small intestine is to absorb nutrients. Choice A is incorrect because the gallbladder stores bile, not the small intestine. Choice C is incorrect because the digestion process primarily occurs in the stomach and small intestine. Choice D is incorrect because while the small intestine does play a role in enzyme production, its primary function is nutrient absorption.