Viroids are the smallest infectious pathogens known. They are solely composed of a short strand of circular, single-stranded RNA without protein coat. All known viroids are inhabitants of higher plants, in which most cause diseases, some of which are of slight to catastrophic economic importance.As cogently expressed by Flores et al: Viruses (and viroids) share the most characteristic property of living beings: In an appropriate environment, they are able to generate copies of themselves, in other words, they are endowed with autonomous replication (and evolution). It is in this framework where viroids represent the frontier of life (246 to 467nt), an aspect that should attract the attention of anybody interested in biology.
The answer to the above question:B