Vector-borne transmission occurs when an infectious agent is transmitted to a host by a vector such as a mosquito, flea, or tick.

• A. A vector carries the pathogen through the air.
• B. An infectious agent is transmitted to a host by fluids only.
• C. An infectious agent is transmitted to a host by a vector such as a mosquito, flea, or tick.
• D. A host becomes infected by ingestion of contaminated water.

Answer: (C)

The main idea is that vector-borne transmission needs a living vector to carry and deliver the pathogen to a host, usually through a bite. A mosquito, flea, or tick acquires the infectious agent from one host and then injects or inoculates it into another, often after the pathogen has multiplied within the vector. This route is different from spreading via air, direct fluids alone, or consuming contaminated water, which are other transmission modes not involving a biting vector. Examples like malaria (mosquito), Lyme disease (tick), and plague (flea) illustrate how the vector is the crucial link in transferring the agent to the host.