Answer: erosion. Erosion is the process in which a natural agent removes material from one location to another location. Another answer could be humans. A good example is the great wall of china! The great wall of china is slowly crumbling because so many tourists step foot on it which could carry the wall's rocks or just destroy the wall. This is technically erosion but man-made.
Explanation:
Which Buffers are you referring too?
Passive immunity because animals are passive.
