What is the role of a vector in the transmission of diseases?

The correct answer is that a vector carries and transmits pathogens. Vectors are often organisms, such as mosquitoes or ticks, that do not cause disease themselves but facilitate the spread of diseases by transferring pathogens from one host to another. For example, when a mosquito bites a human, it can transmit the virus or parasite it carries, thereby leading to disease in the human. This process is crucial in the epidemiology of many infectious diseases, as vectors play a significant role in facilitating the transmission cycle. Understanding this role aids in developing strategies for controlling diseases by targeting the vectors involved. The other options describe different biological roles or immune responses that do not accurately represent the function of vectors in the disease transmission process.