Given the question: Given the following passage  "The genome size, and the number of genes it encodes varies widely between organisms. The smallest genomes occur in viruses (which can have as few as 2 protein-coding genes), and viroids (which act as a single non-coding RNA gene). Conversely, plants can have extremely large genomes, with rice containing >46,000 protein-coding genes. The total number of protein-coding genes (the Earth's proteome) is estimated to be 5 million sequences.",  answer the following question. Note that the answer is present within the text.  Question: Which has a smaller genome, a virus or a viroid?
The answer is:
viroids