Question

identify the following as a first, second, or third line of immune defense.
first second third
tears
phagocytosis
adaptive response

Explanation:

• Tears are physical/chemical barriers (first line of defense).
• Phagocytosis is a non-specific cellular response (second line).
• Adaptive response uses specific immune cells (third line).

Answer:

tears: first
phagocytosis: second
adaptive response: third