The respiratory membrane is a combination of ?

RBC membranes and endothelial cell membranes
respiratory bronchioles and alveolar ducts respiratory bronchioles and alveolar sacs alveolar and capillary walls and their fused basement membranes
atria and alveolar sacs

alveolar and capillary walls and their fused basement membranes

The correct answer is alveolar and capillary walls and their fused basement membranes. The respiratory membrane is made up of the thin walls of the alveoli (alveolar walls) and the walls of the capillaries that surround the alveoli. These two layers are separated by a thin basement membrane, which helps facilitate the exchange of gases between the lungs and blood.