One of the major ways in which the blood is able to defend the body against disease causing organisms is

Analyze the question: It asks how blood defends the body against disease-causing organisms (pathogens). So we need the option that describes a defensive function of blood.

Explain the concept: Blood defends the body in several ways:

• White blood cells (phagocytes) engulf and destroy germs (phagocytosis).
• Lymphocytes produce antibodies.
• Antibodies can cause pathogens to clump together (agglutination), making them easier for phagocytes to destroy.
• Platelets help the blood clot at wounds, sealing the entry points so germs can't get in.

Check each option:

• A. Absorption of fatty acids and glycerol is a digestive process that happens in the lacteals of the small intestine. It has nothing to do with defence.
• B. Clumping is agglutination, where antibodies make pathogens stick together for destruction. Blood clotting is also sometimes described as clumping of blood cells and platelets to seal wounds. This is a defensive function.
• C. Single circulation describes the blood flow pattern in fish (the heart pumps blood once per circuit). It is not a defence mechanism.
• D. Translocation is the transport of manufactured food in the phloem of plants. It is unrelated to blood.

Answer: Only option B relates to the blood's defence against pathogens.

Tip: In JAMB Biology, when you see "defence by blood", think of phagocytosis, antibody production, agglutination (clumping) and clotting. Eliminate options that belong to other systems, such as digestion (A), fish circulation (C) or plant transport (D).