Lungs do not collapse between breaths and some air always remains in the lungs which can never be expelled because?

1. there is a negative pressure in the lungs
2. there is a negative intrapleural pressure pulling at the lung walls
3. there is a positive intrapleural pressure
4. pressure in the lungs is higher than the atmospheric pressure

Subtopic:  Respiratory System: Trachea & Basic Anatomy of Lung |
 55%
Level 3: 35%-60%
NEET - 2016
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