Final answer:
The eosinophil is the blood cell that mainly defends against parasites.
Step-by-step explanation:
The type of blood cell that primarily defends against parasites is the eosinophil. Eosinophils are a type of white blood cell that are involved in the immune response against parasites, particularly helminths (worms) and certain types of allergens. They release toxic granules that are effective in killing and digesting the parasites.
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