Question

what are biological agents?
living things that can cause mutations
non - living physical things that can cause mutations
non - living chemical things that can cause mutations

Explanation:

Biological agents are living organisms. Mutagens are substances that cause mutations. Among the options, only "living things that can cause mutations" fits the definition of biological agents as they are living entities (e.g., certain viruses) that can induce mutations. Non - living physical (e.g., radiation) or chemical (e.g., some chemicals) things that cause mutations are not biological agents.

Answer:

living things that can cause mutations