Commercial cold packs are usually covered with a ________ prior to application

Which of the following structures FIRST allows gas exchange as air enters the lungs?

A) Respiratory bronchioles B) Alveolar ducts C) Alveolar sacs D) Terminal bronchioles

A ppo

A) is a delivery network B) does not receive premiums or assume financial risk C) decreases cost of service if a preferred provider is used D) represents all of the above