The nurse is reinforcing education to the parents of a toddler diagnosed with bronchiolitis. The nurse informs the parents that which of the following is the most common cause of bronchiolitis?

A. Respiratory Syncytial Virus (RSV) is the most common cause of bronchiolitis, particularly in infants and toddlers. B. Haemophilus influenzae type B causes epiglottitis and other respiratory infections but is not a leading cause of bronchiolitis. C. Adenovirus can cause respiratory infections but is not the primary pathogen for bronchiolitis. D. Rhinovirus causes the common cold but is not typically responsible for bronchiolitis.