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Science

Answer:
4. ring of cartilage help to ensure that the air passage does not collapse
each bronchiole terminates into a sac called Alveolar sac it is surrounded by an network of blood capillaries exchange of gases takes place in a the alveoli oxygen from the inhaled air diffuse into the blood while CO2 from the blood diffuse into the alveoli
lungs : a pair of of lungs are present in the thoracic activity lungs are spongy,elastic bags consisting of bronchi ,bronchioles,alveoli