If You Wanted to Show That an Infectious Agent Is

If you wanted to show that an infectious agent is a virus, what experiment could you do?

A) Show that the agent can be seen under a light microscope.
B) Show that agent contains a lipid membrane.
C) Show that the agent can form single colonies on an agar plate.
D) Show that the agent can be diluted and can still cause disease in an animal.
E) Show that the agent can pass through a porcelain filter and is still infectious.