The correct answer is (d) A virus that attack bacteria
The virus that infects bacteria is called bacteriophage. The virus invades the body of bacteria and infects it. The bacteria becomes the host for the virus to live in and the virus incorporates its DNA into the DNA of the bacteria and starts replicating inside bacteria. The literal meaning of bacteriophage is" bacteria eater". These bacteria that are infected by the virus are harmful to the human body as they cause diseases. The virus infected bacteria such as Vibrio cholerae causes cholera and Shigella which causes dysentery are some example of bacteriophage.
