Respuesta :

unknown4191
they give the lungs a really big surface area
they have moist, thin walls (just one cell thick)
they have a lot of tiny blood vessels called capillaries

Answer:  

they give the lungs a really big surface area.

they have moist, thin walls (just one cell thick)

they have a lot of tiny blood vessels called capillaries.

Hopes this helps :D

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