The Quaternary was not a period of the Mesozoic.
The best answer is A.
In a lysogenic cycle, the viral DNA or RNA enters the cell and integrates into the host DNA as a new set of genes called prophage. The prophage is passive and non virulent and does not destroy the cell. However if the prophage undergoes any stress or mutation or is exposed to UV radiation, it may adopt the lytic cycle and become infective.
In a lysogenic infection, there are no viral symptoms and it occurs after the viral infection is over. But the viral DNA or RNA remains in the cell and may remain there permanently .
They do it seasonally- usually in warm temperatures
