Answer:
The correct answer would be D.Alveolar sacs are surrounded by thin capillaries where gases can be exchanged.
Alveoli are tiny sacs which form the site of gas exchange in the lungs.
The features of alveoli which help in gas exchange are:
- They increase the surface area in the lungs thus, more space is available for gas exchange.
- They have very thin walls, as thin as the thickness of a single cell only.
- They are surrounded by a bunch of thin capillaries which exchange gases with alveoli.
The protein components which reside on the red blood cell membrane and which determines blood type are THE ANTIGENS.
Antigens are proteins molecules which are found on the surface of the red blood cell, the antigens that are present in the cell determine the type of blood that will be present in the individual. There are four types of blood; A, B, AB and O. <span />
I believe the answer is a
