This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
True about viroids is?a) Cause tumors in animalsb) Lack envelope like coveringc) Have only genetic materiald) Visible on light microscope 
Select and explain. 
A. bc, B. c, C. ac, D. ad
A: bc
Answer: A: bc 
Explanation: None