Final answer:
Granulocytes are a type of white blood cell characterized by granules in their cytoplasm, contributing to the immune response (option b).
Step-by-step explanation:
Granulocytes are a type of white blood cell (leukocyte) that are important in the body's immune response. They are characterized by the presence of granules in their cytoplasm and a lobed nucleus. Granulocytes include different cell types such as neutrophils, eosinophils, and basophils, which are all involved in the immune response, particularly as first responders to injury or infection. The other main grouping of white blood cells is the agranulocytes, which include lymphocytes and monocytes.
Therefore, granulocytes are white blood cells and the correct answer to the student's question is option (b) leukocytes.