Although Prion Infectious Agents Are More Closely Related to Viruses

Although prion infectious agents are more closely related to viruses than any other kind of infectious agents, there are still some major differences between the two. Which statement describes a major difference?

A) Viral infections can always be treated and cured, whereas prion diseases cannot.
B) Viruses can be transmitted by animal to human or human to human, but prions are always human to human transmission.
C) Prions are not destroyed by heat, but viruses can be inactivated by heat.
D) Viruses do not contain protein, whereas prions do.