One virus paicle prevents multiplication of second virus. This phenomena is -

Ans. is 'a' i.e., Viral interference Interference . In a mixed or multiple infection of cells, in which infection of a cell by one virus inhibits simultaneous or subsequent infection by another virus is called Interference. . The most impoant mediator of interference is interferon. . A high multiplicity of infection inhibits production of its own infectious progeny - autointerference Viral interference has been applied in the field in Controlling poliomyelitis by live attenuated vaccine.