Protein-energy malnutrition (PEM) may be responsible for the increased incidence of noma and necrotizing ulcerative gingivitis (NUG) because these conditions are associated with depressed immune responses caused by nutritional deficiencies.

Correct Answer: A

Rationale: The corrected question highlights that protein-energy malnutrition weakens the immune system, making individuals more susceptible to conditions like noma and NUG, which are linked to compromised immunity. Choice A is correct because the statement and reason are both accurate and directly related. Protein-energy malnutrition does result in depressed immune responses, which can predispose individuals to noma and NUG. Choice B is incorrect because the statement and reason are indeed related. Choice C is incorrect as both the statement and reason are accurate. Choice D is also incorrect as the statement is correct and directly supports the reason provided.

Correct Answer: A

Rationale: The correct answer is an ionic bond. An ionic bond is formed when a positively charged metal ion joins with a negatively charged nonmetal ion, resulting in a transfer of electrons. In contrast, a covalent bond involves sharing electrons between atoms rather than complete transfer. Functional groups are specific groups of atoms within molecules that determine the molecule's chemical properties. Metallic bonds occur between metal atoms where electrons are shared across a delocalized electron cloud.

Correct Answer: C

Rationale: The correct answer is C. The bolus is not transported to the stomach by osmosis and gravity, but by peristalsis. Peristalsis is the involuntary constriction and relaxation of muscles to push the bolus through the digestive system. Choices A, B, and D are correct statements. A bolus is indeed a mass of food, the swallowing reflex does move the bolus into the esophagus, and the bolus does not penetrate the diaphragm through the esophageal hiatus; instead, it enters the stomach through the lower esophageal sphincter.

Correct Answer: C

Rationale: Lamivudine belongs to the class of nucleoside reverse transcriptase inhibitors (NRTIs), making choice C the correct answer. NRTIs like lamivudine work by inhibiting the reverse transcriptase enzyme, an essential component for the HIV virus to replicate. Choices A, B, and D are incorrect because lamivudine does not function as a CCR5 antagonist, fusion inhibitor, or protease inhibitor in the management of HIV infection.

Correct Answer: B

Rationale: Anticoagulants are the most suitable choice for a patient following a myocardial infarction. These medications are essential in preventing further blood clots from forming in the arteries, reducing the risk of complications such as strokes or recurrent heart attacks. Antiemetics are used to control nausea and vomiting, not directly related to myocardial infarction. Anticonvulsants are used to manage seizures, not typically indicated after a heart attack. Antibiotics are prescribed to treat bacterial infections, not routinely given after a myocardial infarction.