Correct Answer: A

Rationale: Projectile vomiting is the hallmark clinical manifestation of pyloric stenosis in infants. In pyloric stenosis, the muscle surrounding the opening between the stomach and the small intestine thickens, leading to obstruction. This obstruction causes forceful, projectile vomiting, which is typically non-bilious (does not contain bile) and occurs after feedings. Choices B, C, and D are incorrect because diarrhea, constipation, and abdominal distension are not typical symptoms of pyloric stenosis.

Correct Answer: D

Rationale: Recognizing signs of hypoglycemia is essential for managing type 1 diabetes mellitus. Hypoglycemia, which occurs when blood glucose levels drop too low, can be dangerous and requires immediate intervention to prevent severe complications. Monitoring blood glucose levels more frequently than once a day, following a strict meal plan, and administering insulin only when blood glucose is high are important aspects of diabetes management but recognizing signs of hypoglycemia is crucial as it enables prompt action to prevent adverse outcomes.

Correct Answer: A

Rationale: Trisomy 21, also known as Down syndrome, is caused by nondisjunction, which is an error in cell division that leads to the presence of an extra chromosome 21. This additional chromosome alters the normal genetic makeup, resulting in the characteristics associated with Down syndrome. Therefore, the correct answer is nondisjunction (Choice A). Choices B, C, and D are incorrect because Trisomy 21 is not caused by X-linked recessive inheritance, genomic imprinting, or autosomal dominant inheritance. Understanding the specific genetic mechanism involved in Trisomy 21 is crucial for grasping the basis of this chromosomal disorder.

Correct Answer: A

Rationale: The correct answer is to advise the parents to avoid exposure to allergens. Asthma attacks are commonly triggered by allergens such as pollen, dust mites, pet dander, and mold. By minimizing the child's contact with these triggers, the likelihood of asthma attacks can be reduced. Encouraging regular exercise can be beneficial for overall health but may not directly prevent asthma attacks. Providing a high-protein diet and increasing fluid intake are important for general health but are not specific preventive measures for asthma attacks.

Correct Answer: A

Rationale: The correct answer is to advise the parents to avoid exposure to allergens. Asthma attacks are often triggered by allergens such as dust mites, pollen, pet dander, and mold. By minimizing the child's exposure to these triggers, the likelihood of asthma attacks can be reduced. Encouraging regular exercise is beneficial for overall health but may not directly prevent asthma attacks. Providing a high-protein diet and increasing fluid intake are important for general well-being but do not specifically address asthma prevention.