Vectors are the agents that act as carriers of a pathogen and spread diseases. They play a crucial role in the transmission of various infectious diseases from one host to another. Vectors can be classified into different categories, including arthropods (such as mosquitoes, ticks, and fleas), mammals (such as bats and rodents), and birds.

Vectors transmit diseases by carrying the pathogen from an infected host to a susceptible host. This can occur through various mechanisms, such as biting, feeding, or direct contact with body fluids. When a vector bites an infected host, it ingests the pathogen along with the blood. The pathogen then infects the vector's body and replicates within it. Subsequently, when the vector feeds on a new host, it injects the pathogen into the bloodstream, thereby transmitting the disease.

Some common vector-borne diseases include malaria, dengue fever, Zika virus, Lyme disease, and West Nile virus. These diseases are prevalent in many parts of the world and can have significant health impacts on individuals and communities.

Vectors are particularly effective in transmitting diseases because they can travel long distances, have a wide distribution, and often have a high reproductive rate. Additionally, some vectors can transmit multiple diseases, further contributing to the spread of infections.

Preventing and controlling vector-borne diseases involve various strategies, including vector control measures, such as the use of insecticides, mosquito nets, and environmental modifications. Vaccination, personal protective measures (such as wearing long sleeves and using insect repellents), and public health education also play important roles in reducing the risk of vector-borne diseases.

In conclusion, vectors are agents that carry pathogens and spread diseases. They are responsible for the transmission of many infectious diseases and pose a significant public health challenge. Understanding the role of vectors in disease transmission is crucial for developing effective prevention and control strategies.

Answer is C