Final answer:
The nurse would expect the parents to report if the infant has had a) projectile vomiting.
Step-by-step explanation:
The nurse interviewing parents of an infant with pyloric stenosis would expect the parents to report if the infant has had projectile vomiting. Projectile vomiting is a key symptom of pyloric stenosis, a condition where the opening between the stomach and small intestine becomes narrowed, leading to forceful and sometimes projectile vomiting.