Final answer:
D. Macrophages. Macrophages are primarily responsible for the formation of granulomas in response to Mycobacterium infection.
Step-by-step explanation:
The cells primarily responsible for the formation of granulomas in response to Mycobacterium infection are macrophages. Macrophages are a type of phagocyte that can both phagocytize pathogens and produce chemicals that promote inflammation. They play a key role in the immune response to Mycobacterium tuberculosis infection, recruiting other immune cells and forming granulomas to contain the infection.