Correct Answer: D

Rationale: The correct answer is D. Infants have a higher extracellular fluid requirement per unit of body weight, making them more susceptible to dehydration and electrolyte imbalances during illnesses such as diarrhea. Choice A is incorrect as cellular metabolism instability does not directly relate to the infant's condition described. Choice B is inaccurate as the proportion of water in the body is not the primary issue causing the infant's symptoms. Choice C is incorrect as renal function being immature does not explain the sudden change in the infant's health status; it is more related to fluid balance and dehydration.

Correct Answer: B

Rationale: The correct answer is B: Signs of child abuse. Large welts and scars on a child may be indicative of abuse, making it crucial for the nurse to assess and report any suspicions. Assessing the history of an injury (choice A) may not provide insight into the cause of the welts and scars as effectively as looking for signs of potential abuse. Food allergies (choice C) and recent recovery from chickenpox (choice D) are not directly relevant to the observation of welts and scars on the child's back.

Correct Answer: C

Rationale: Administering antibiotics is crucial post-tonsillectomy to prevent infection, as the surgical site is susceptible to bacterial growth. Encouraging deep breathing exercises can also be beneficial for lung expansion and preventing respiratory complications. However, administering antibiotics takes precedence as it directly addresses the risk of infection. Encouraging the child to eat may not be appropriate immediately post-tonsillectomy due to the risk of throat irritation and potential discomfort. Applying ice to the throat is typically not recommended after a tonsillectomy, as it may constrict blood vessels and hinder the healing process.

Correct Answer: B

Rationale: Chest tubes are necessary after open-heart surgery to facilitate the drainage of air and fluid from the chest cavity. These tubes help prevent complications such as pneumothorax (accumulation of air in the pleural space) or cardiac tamponade (build-up of fluid in the pericardial sac), which can be serious postoperative issues. Options A, C, and D are incorrect because chest tubes are primarily used for draining purposes and not for increasing tidal volumes, maintaining positive intrapleural pressure, or regulating pressure on the pericardium and chest wall.

Correct Answer: C

Rationale: In a child diagnosed with acute glomerulonephritis, monitoring urine output is a crucial assessment. Acute glomerulonephritis affects the kidneys, leading to decreased urine output due to impaired kidney function. Monitoring urine output helps assess renal perfusion, fluid status, and kidney function. This assessment is essential in determining the effectiveness of treatment and identifying complications. Monitoring blood glucose levels (Choice A) is not directly related to acute glomerulonephritis. Respiratory rate (Choice B) may be important in other conditions but is not a key assessment for acute glomerulonephritis. Monitoring for signs of infection (Choice D) is important in general, but it is not specific to the primary issue of impaired kidney function in acute glomerulonephritis.