This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Human Immunodeficiency Virus, Subject name: Microbiology
Prions are: 
Select and explain. 
A. Made up of bacterial and viral particles, B. Immunogenic, C. Infectious, D. RNA particles
C: Infectious
Answer: C: Infectious 
Explanation: Ans. is 'c' i.e., InfectiousPrions are small protein-containing infectious particles with no detectable nucleic acid. They were suspected to be viruses but otherwise do not conform to the standard definition of viruses. They differ from the viruses in their many properties. The prions show following characteristics:1. Prions like viruses are filterable.2. They apparently lack any virion structure or genome.3. Unlike viruses, they are unusually resistant to inactivation by heat, disinfectants and radiation.4. They do not elicit any specific immune response in the infected host.