What is an antibiotic?

An antibiotic is defined as a chemical produced by microorganisms that has the ability to kill or inhibit the growth of other microorganisms. This definition aligns with the correct answer choice. Antibiotics specifically target bacteria and are utilized primarily in medical contexts to treat bacterial infections, although their mechanisms can also be applicable in agriculture for managing bacterial diseases in plants.

The other choices do not accurately represent what an antibiotic is. For example, a chemical that enhances pesticide effectiveness focuses on improving the performance of pesticides rather than addressing the interaction between microorganisms. A fertilizer used in agriculture serves a different purpose, as it is aimed at providing essential nutrients to plants rather than targeting microorganisms. Similarly, a synthetic pesticide refers to manufactured chemicals designed to manage pests, which is distinctly different in function and composition from antibiotics. Understanding these key distinctions helps clarify the role and nature of antibiotics in both health and agricultural practices.