This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
Non-coding RNAs are 
Select and explain. 
A. siRNA, B. miRNA, C. tRNA, D. mRNA
A: siRNA
Answer: A: siRNA 
Explanation: A non-coding RNA (ncRNA) is a functional RNA molecule that is transcribed from DNA but not translated into proteins. Epigenetic related ncRNAs include miRNA, siRNA, piRNA, and lncRNA. In general, ncRNAs function to regulate gene expression at the transcriptional and post-transcriptional level.