In humans, gas exchange and gas transport occur as a result of the functioning of a system of

a: phloem tubes
b: lungs and blood vessels
c: ganglia
d: setae

The answer is B) Lungs and blood vessels. 
the blood take fresh oxygen throughout the body and removes the old. the lungs give the oxygen to the blood

B.) lungs and blood vessels.

- When we inhale atmospheric air, through the nose it go to the trachea and then via bronchus and bronchioles it ultimately go to the alveolus where exchange of different gas takes place.

               --hope that i helped you very well--

The answer is b. hope this !

This is the most closely resembles the model.