35 POINTS!!!!!!

In the image above of an alveolus, what is the identity of the two visible tissue layers labeled C and D.

AC = inner wall of alveolar sac; D = outer wall of alveolar sac

BC = inner wall of alveolar sac; D = outer capillary wall

CC = outer wall of alveolar sac; D = outer capillary wall

DC = inner capillary wall; D = outer capillary wall