A toddler has had recurrent respiratory infections. The mother of the child expressed concern that her child seemed to be at increased risk for complications from infection in comparison with her older children. What is the best response from the nurse?

"Air passages are more likely to become blocked with mucus because younger children make more mucus than do older children."

"Airways structures are closer together so infection spreads faster in the young child."

"Younger children have more exposure to respiratory illnesses."

"Toddlers do not breathe as deeply as do older children."