Please answer only Q#3, noneed of #4
Blood Typing questions
The key to understanding blood typing is to remember what the letters stand for. The letter "A" stands for a specific type of protein found on the surface of red blood cells (RBCs). Likewise, "B" stands for a different type of protein. These proteins are called antigens (because they can trigger an antibody immune response). The letter "O" indicates that neither the A nor the B protein are found. Think of "O" as being "nOthing."
In addition to this fact is the importance of understanding antibody production. If someone does not have "A" in their blood, then when ...
Blood typing questions are thoroughly discussed.