Which Is an Example of a Specific Line of Defense

Multiple Choice

Which is an example of a specific line of defense against an infectious agent?

A) The skin acts as a barrier to infection by the agent.
B) Macrophages engulf the invading agent in the affected tissue.
C) Mucus membranes in the lungs trap the invading pathogens.
D) B cells stick to the invading pathogen's surface.