Key features of phagocytosis in immune responses Steps:

• Phagocytosis is performed by innate immune cells like macrophages that engulf pathogens.
• These cells undergo mitosis to expand their population during infection.
• Phagocytosis activates adaptive immunity, leading to production of memory cells for long-term protection.
• Recognition and enzyme secretion occur but are not exclusive to the core phagocytic process as defined here.

Why D is correct:

• Phagocytosis involves mitotic proliferation of phagocytes and triggers memory cell formation in linked adaptive responses, per immune system activation pathways.

Why the others are wrong:

• A includes 4 (enzyme secretion), which aids digestion but is not a primary phagocytic response.
• B includes 2 (recognition), a general step not specific to phagocytosis execution.
• C includes 2 (recognition), overlooking mitosis and misapplying it without proliferation.

Final answer: D