Final answer:
Increased work of breathing and tachypnea in a toddler may be classified as Bronchiolitis (option 3).
Step-by-step explanation:
Increased work of breathing and tachypnea in a toddler may be classified as BronchHIOlitis (option 3). Bronchiolitis is a common viral infection that causes inflammation and narrowing of the small airways in the lungs, specifically the bronchioles. This can lead to difficulty breathing and rapid breathing in toddlers. Asthma (option 1) and pneumonia (option 2) are also respiratory conditions, but they are not specifically indicated by the symptoms described in the question.