Correct Answer: A

Rationale: Renin is the correct answer. When arterial blood pressure decreases, the kidneys release renin, which triggers a series of reactions ultimately leading to an increase in blood pressure and peripheral resistance. Antidiuretic hormone (choice B) is involved in water retention, atrial natriuretic hormone (choice C) promotes sodium excretion and lowers blood pressure, and insulin (choice D) regulates glucose metabolism, not blood pressure.

Correct Answer: C

Rationale: The correct answer is C. Osteoporosis is commonly caused by bone loss that occurs with aging, leading to brittle bones. Choice A, poor nutrition in infancy, is not a direct cause of osteoporosis. Choice B, regularly weight-bearing exercise, actually helps in maintaining bone density and strength, reducing the risk of osteoporosis. Choice D, cerebral palsy and associated disorders, is not a common cause of osteoporosis.

Correct Answer: C

Rationale: The correct answer is C: Increased red blood cells being produced. Polycythemia is a condition characterized by an elevated number of red blood cells in the blood. This increased concentration of red blood cells can lead to blood thickening and potentially result in complications such as blood clots. Choices A, B, and D are incorrect because polycythemia does not involve deficient plasma, increased lymphatic fluid production, or a deficient number of red blood cells.

Correct Answer: A

Rationale: The correct answer is A: Ventilation. Ventilation is the process of moving air into the lungs and distributing it to the alveoli for gas exchange. Choice B, Aeration, is not the correct term for this specific process. Choice C, Enclosure vapor, is not related to the movement of air into the lungs. Choice D, Residual volume, refers to the amount of air left in the lungs after maximal expiration and is not the process of moving air into the lungs.

Correct Answer: A

Rationale: The symptoms of headache, vomiting, blurred vision, and loss of consciousness following a concussion are indicative of increased intracranial pressure. These symptoms are commonly associated with intracranial pressure elevation, which can be dangerous and requires immediate medical attention. Lower extremity compartment syndrome is characterized by severe pain and swelling in the affected limb, not the symptoms mentioned. Consuming too much food at once may lead to digestive issues but does not correlate with the symptoms described. Improved kidney function would not manifest through the symptoms mentioned after a concussion.