This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Test for quantification of viral infectivity is \nSelect and explain. \nA. Cytopathic effect, B. Plaque assay, C. Electron microscopy, D. Haemagglutination', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Viral assays\n\nVirus content of a specimen can be assayed in two ways\n\n1. With reference to total virus particles-\n\nElectron microscopy\nHemagglutination\n\n2. With reference to the infectious virions only\nA. Quantal Assays\n→ Indicates the presence or absence of infectious virus e.g\n\nDeath of the experimental animal.\nProduction of haemagglutinin in allantoic fluid.\nAppearance of cytopathological effects on cell cultures.\n\nB. Quantitative infective assay\n\nIt measures the exact number of infectious particles. Eg:\nPlaque assay (monolayer cell culture) (CAM).\nPock assay on chick embryo chorioallantoic membrane.\n\n→\xa0Viruses producing pocks on chorioallantoic membrane are HSV, vaccinia, smallpox (variola), monkey pox, cowpox and camel pox.', 'role': 'assistant'}]