Choice A reason: Dehydration is a common and serious complication of rotavirus gastroenteritis, which causes vomiting, diarrhea, and loss of fluids and electrolytes. The nurse should monitor the infant's intake and output, weight, vital signs, skin turgor, mucous membranes, fontanelles, and urine specific gravity.

Choice B reason: Hypoglycemia is not a typical complication of rotavirus gastroenteritis, unless there is severe malnutrition or insulin overdose. The nurse should monitor the infant's blood glucose levels if indicated by signs such as lethargy, jitteriness, or seizures.

Choice C reason: Hyperkalemia is not a typical complication of rotavirus gastroenteritis, unless there is renal failure or excessive potassium intake. The nurse should monitor the infant's serum potassium levels if indicated by signs such as muscle weakness, arrhythmias, or cardiac arrest.

Choice D reason: Metabolic alkalosis is not a typical complication of rotavirus gastroenteritis, unless there is excessive vomiting or bicarbonate intake. The nurse should monitor the infant's serum pH and bicarbonate levels if indicated by signs such as confusion, tremors, or tetany.