The doctor examines a premature newborn baby. Objectively observed single apnea lasting up to 5 seconds. What is the main functional feature respiratory system can explain the attacks of apnea in a premature baby?

Answer options

1. Softness of tracheal and bronchial cartilage
2. Predisposition of mucous membranes to edema and hypersecretion
3. Narrowness of the airway
4. Functional immaturity of the respiratory center
5. Insufficient drainage and protective function of the bronchi