I think the correct answer from the choices listed above is option A. It is the alveoli that is composed of single layer <span>surrounded by a network of capillaries. These are used to allow oxygen and carbon dioxide to move from the lungs to the bloodstream.</span>
Arrow a should point to muscle tissue, arrow B should point to an organ, arrow c should point to organ system.
All of these are body regions.
Antecubital, brachial, crural, and femoral regions are ventral/anterior appendicular body regions.
Axillary region is ventral/anterior axial body region.
Popliteal and sural body regions are dorsal/posterior appendicular body regions.
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