Which of the following best describes a common symptom in infants that requires monitoring?

Acrocyanosis is a common and often benign condition observed in infants, characterized by a bluish discoloration of the hands and feet. It typically occurs as a result of peripheral circulation issues but doesn't typically indicate a serious underlying problem, especially if it resolves when the infant is warmed. While acrocyanosis requires monitoring, it is usually not a cause for immediate concern unless it persists or is accompanied by other symptoms.

In contrast, excessive weight gain, while it can indicate overfeeding or other issues, may not require immediate monitoring in the sense of acute patient safety. Persistent vomiting in infants can be a sign of more serious conditions, such as gastrointestinal obstruction or infection, and would necessitate more urgent intervention. Difficulty breathing is clearly a dangerous symptom that demands immediate medical attention due to the risk of respiratory distress or failure. Given this context, acrocyanosis is a common symptom that merits observation, but it's less critical than the more severe symptoms associated with persistent vomiting or difficulty breathing.