Which of the following statements is correct about the ABO blood group system?

Step 1: Analyze the question The question asks which statement correctly describes where antigens and antibodies are found in the ABO blood group system.

Step 2: Key concept

• Antigens (A and B) are protein/carbohydrate markers found on the surface of red blood cells (RBCs).
• Antibodies (anti-A and anti-B) are found in the blood plasma.

| Blood group | Antigen on RBC | Antibody in plasma | |---|---|---| | A | A | anti-B | | B | B | anti-A | | AB | A and B | none | | O | none | anti-A and anti-B |

Step 3: Check each option

• A. Antigens on white blood cells. Wrong. In the ABO system, the antigens are on red blood cells.
• B. Antibodies in the blood plasma. Correct. Anti-A and anti-B antibodies are dissolved in the plasma.
• C. Antibodies on the surface of red blood cells. Wrong. That is where the antigens are, not the antibodies.
• D. Antigens in the blood plasma. Wrong. Antigens are on the RBC surface.

Step 4: Answer

Tip: Remember "Antigens are on the Animal cells (RBCs); Antibodies are in the plasma (fluid)." Another way: antiGens = Gate (surface), antiBodies = Body fluid (plasma).