A 9 month old presents to clinic with 2 days history of acut…

A 9 month old presents to clinic with 2 days history of acute, intermittent cough without fever, stridor, retractions, or cyanosis. Cough start 2 evenings ago after dinner. On exam, well-appearing with intermittent dry cough, no retractions, prominent xyphoid process.  Wheezing heard at the RML that does not resolve with coughing. Your differential diagnosis includes foreign body, asthma, bacterial pneumonia.  You are most suspicious for foreign body because which anatomical risk factor?