B. Write down the major functions of blood circulatory system.

The circulatory system is responsible for many functions that we perform.

it transports oxygen and nutrient throughout the human body.

The blood carries useful substances to the cells and takes away the waste products of the cells, which include urea, carbon dioxide and other metabolic wastes.

blood carries white blood cells and platelets, which help protect the body by clotting wounds and fighting off pathogens.

Hope this helps (●'◡'●)

An immune system identifies a pathogen by recognizing molecules on the surface of the microbe called epithelials. These cells send signals to the cytoplasm to produce chemicals called lipopolysaccharides that bind to the antigen and mark the pathogen for destruction. Other immune cells attack the target pathogen by detecting its immune system.

Explanation:

Innate cell recognition systems are based on surface or intracellular proteins of epithelial cells, neutrophils, macrophages, and dendritic cells and on soluble cytoplasmic receptors. All these receptors are generally called PRRs (Pattern Recognition Receptors) and bind to PAMPs (Pathogen-associated Molecular Patterns) molecules expressed only by the pathogen (bacterial lipopolysaccharides, carbohydrates and lipoproteins, peptidoglycans, RNA, DNA, etc.) thus as for the commensal flora.