This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology, Subject name: Microbiology
Viroids are ? 
Select and explain. 
A. ssRNA, B. DNA from matric proteins, C. Naked pathogenic human viruses, D. Fragments of viruses
A: ssRNA
Answer: A: ssRNA 
Explanation: Genome much smaller than those of known virus. Agent is a protien free low molecular wt RNA REF:ANANTHANARYANAN TEXT BOOK OF MICROBIOLOGY 9EDITION PDNO.442