Infectious agent is transmitted to susceptible host from -

Ans. is 'd' All of these Actually infectious agent can be transmitted to susceptible host by all the given options.But all are then classified as source of infection to the host.Source is 'the person, animal, object or substance from which infectious agent passes to host', i.e. man acquires infection from source.Reservoir is 'any person, animal, insect, plant, soil or substance in which an infectious agent lives and multiplies'.Infectious agent is dependent on reservoir for survival. From reservoir it can be transmitted to susceptible host.Thus a reservoir may act as a source of infection when a person acquires infection directly from a reservoir.