Correct Answer: D

Rationale: Calcium absorption in the small intestine relies heavily on vitamin D, which enhances the process by increasing the expression of calcium-binding proteins and improving gut uptake efficiency. Without adequate vitamin D, calcium absorption drops significantly, leading to potential bone health issues like osteoporosis or osteomalacia. Intrinsic factor, produced in the stomach, is critical for vitamin B12 absorption, not calcium, as it binds B12 for uptake in the ileum. Coenzymes, while involved in metabolic reactions, don't directly facilitate calcium absorption; their role is broader and unrelated to this specific process. Phosphorus, an abundant mineral, works with calcium in bone formation but doesn't enhance its absorption-in fact, excessive phosphorus can compete with calcium. Vitamin D's active form, calcitriol, regulates calcium levels by promoting its transport across intestinal cells, making it indispensable for maintaining skeletal integrity. This mechanism underscores why vitamin D deficiency impairs calcium utilization, distinguishing it from the other options, which lack a direct link to absorption efficiency.

Correct Answer: B

Rationale: Buspirone requires regular dosing-weeks-to reduce anxiety via serotonin modulation, not PRN like benzos, per pharmacology. Dizziness, headache, drowsiness are true side effects. Regular use is needed for effect. It's non-addictive, unlike benzos. PRN use misstates its action, needing correction.

Correct Answer: A

Rationale: Increasing the temperature does not result in local analgesia. In fact, higher temperatures can often lead to increased pain sensitivity. Local analgesia is achieved through methods such as chemically or physically damaging nerve trunks, stimulating large fiber nerve activity, or rendering tissue anemic. These procedures work by interrupting the transmission of pain signals to the brain or by reducing the sensitivity of local nerve endings to pain stimuli.

Correct Answer: C

Rationale: Levetiracetam treats post-stroke focal seizures by modulating SV2A, offering efficacy, minimal hepatic metabolism, and low interaction risk, ideal for an elderly patient with likely polypharmacy. Phenytoin, a sodium channel blocker, controls seizures but has nonlinear kinetics and P450 induction, risking toxicity. Oxcarbazepine, similar to carbamazepine, has hyponatremia risks, concerning in the elderly. Phenobarbital sedates and interacts via P450. Levetiracetam's safety, renal clearance, and effectiveness in stroke-related epilepsy, per guidelines, make it the most appropriate here.

Correct Answer: D

Rationale: Hypocalcemia causes muscle spasms (tetany)-nerve hyperexcitability, per classic signs-unlike bruising (coagulation), hypertension (not direct), or wasting (chronic). Spasms dominate, per assessment.