<prompt> Growth of virus in embryonated egg, eggs are incubated for -4-8 hours1-2 days5-12 days20-25 days  <response>: Ans. is c i.e., 5-12 days For virus isolation, feile chicken eggs are incubated for 5-12 days, and a viral Suspension or suspected virus - containing tissue is injected into the fluid of the egg. 