The phage which does not destroy the host cell but infects, it is called

A. Cyanophage
B. T2 phage
C. Virulent phage
D. Lambda phage

Hint: A bacteriophage is a phage virus which infects the bacteria and replicates inside the bacterial cell. The bacteriophage virus is composed of DNA or RNA genome that is encapsulated in protein structure. This virus replicates inside the bacteria which injects its genome in the bacterial cytoplasm.

Complete answer:Bacteriophage virus shows two types of infection in bacteria that are named as lytic and lambda (temperate). The phage virus that infects the bacteria and then destroys the bacteria wall is called lytic phage virus, while lambda phage bacteria infect the bacterial cell and incorporate with the bacterial genome and the replicate itself is the lambda phage virus. Cyanophages are the viruses which infect the cyanobacteria or blue-green algae, and they are photosynthetic bacteria. Cyanophage contains double-stranded DNA with the icosahedral head with the tail, and both structures vary among species of Cyanophage. It is found in marine and freshwater. The T2 phage is a type of Enterobacteria phage T2 virus which usually kills or infects E.coli bacteria, their genome is linear double-stranded DNA, which is covered by the protective layer of protein coat. Virulent phage is a lytic type of bacteriophage, and in the lytic cycle, the virus infects the bacteria by involving rupture of lysis of the host cell by releasing several viral progenies. Lambda phage is a temperate phage or lysogenic phage. This type of virus infects the bacterial cell by inserting its genome, which incorporates the host cell and replicates itself, such type of phage virus is lambda phage, this type of phage does not cause harm to the host cell.
Hence the correct option is D.

Note: The lambda phage follows the lysogenic life cycle, and it does not cause the death or lysis of the host, but they integrate their genome into the host bacterial genome. It infects the host genome and replicates with the help of bacterial genome for many generations.