This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Radiotherapy, Subject name: Radiology
Micro RNAs are 
Select and explain. 
A. Involved in post translational gene regulation, B. 20-22 nucleotide length, C. Noncoding RNA, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: MicroRNAs (miRNAs) are small noncoding RNAs 20-22 nucleotides in length that are involved in posttranscriptional gene regulation. Studies in chronic lymphocytic leukaemia first suggested a link between miRNAs and cancer when miR-15 and miR-16 were found to be deleted or downregulated in the vast majority of tumours.The expression of miRNAs is extremely specific and there is evidence that miRNA expression patterns may be useful in distinguishing lineage and differentiation state, as well as cancer diagnosis and outcome prediction.Reference: Harrison; 19th edition