Correct Answer: A

Rationale: Polyarthritis is indeed frequently the initial sign of acute rheumatic fever in children. It presents as joint pain, swelling, and redness. Carditis (inflammation of the heart), Erythema marginatum (a skin rash), and Sydenham chorea (involuntary muscle movements) are typically seen in the later stages of acute rheumatic fever and not as the initial sign.

Correct Answer: B

Rationale: The correct answer is B: Wheezing. Wheezing is a key distinguishing feature of bronchiolitis in infants, typically caused by respiratory syncytial virus (RSV) infection. Bronchiolitis is characterized by inflammation and mucus buildup in the small airways of the lungs, leading to wheezing sounds during breathing. Choices A, C, and D are incorrect because dry cough, stridor, and productive cough are not typical features of bronchiolitis in infants.

Correct Answer: A

Rationale: Administering oxygen is crucial during a sickle cell crisis in a child as it helps to prevent further sickling of cells. Oxygen therapy can improve oxygen saturation levels, reducing the risk of tissue damage and complications. Applying cold compresses (choice B) is not recommended as it can potentially worsen vaso-occlusive crisis by causing vasoconstriction. Restricting fluids (choice C) is not appropriate as hydration is essential to prevent dehydration and maintain adequate blood flow. Encouraging bed rest (choice D) may be necessary but administering oxygen takes precedence in managing a sickle cell crisis.

Correct Answer: C

Rationale: The most common complication following surgical correction of esophageal atresia with tracheoesophageal fistula in infants is stricture formation. This complication occurs due to the healing process after surgery, leading to the narrowing of the esophagus. Gastroesophageal reflux (Choice A) can be a concern but is not the most common complication. Respiratory distress (Choice B) may happen but is not the primary complication. Aspiration pneumonia (Choice D) is a risk but is typically not as common as stricture formation in these cases.

Correct Answer: C

Rationale: Frequent spitting up is indeed a common symptom of gastroesophageal reflux in infants. It is caused by the backward flow of stomach contents into the esophagus, leading to infants regurgitating milk or formula shortly after feeding. Projectile vomiting (choice A) is more commonly associated with conditions like pyloric stenosis rather than gastroesophageal reflux. Bilious vomiting (choice B) often indicates an obstruction in the gastrointestinal tract. Diarrhea (choice D) is not typically a primary symptom of gastroesophageal reflux in infants.