Final answer:
Eosinophils are the type of WBC that responds to allergies and parasitic infections, being particularly active in fighting large parasites and playing a key role in allergic responses.
Step-by-step explanation:
The white blood cell (WBC) that responds to allergies and parasitic diseases is the eosinophil. Eosinophils are a type of granulocyte, which include neutrophils, eosinophils, and basophils. These cells are characterized by a lobed nucleus and granular inclusions in the cytoplasm.
Eosinophils are particularly effective in fighting parasitic infections and playing a key role in the allergic response. They contain granules and can release a range of highly toxic substances to kill large parasites like worms. Moreover, eosinophils can become overactive, leading to allergies or asthma.
In summary, the correct answer to the question about which white blood cell responds to allergies and parasitic disease is d. eosinophil.