Answer: Number 2, aka Solid wastes on land.
Explanation: Bacteria in soil is a natural thing, so it's not polluting the earth. Oxygen in the atmosphere is letting us live, meaning it's not polluting the earth. Fish in rivers is also another natural thing, leaving us with solid wastes on land.
A) a common ancestor
Homologous structures are structures that are similar in related organisms. There is a basic pattern of bones which can be inherited from a common ancestor
