With Respect to MicroRNAs, Which, If Any, of the Following

Multiple Choice

With respect to microRNAs, which, if any, of the following statements, is true?

A) MicroRNA genes often occur in gene clusters within introns of protein-coding genes and are usually transcribed by RNA polymerase II.
B) Like an mRNA a miRNA is initially produced as a larger precursor RNA that, like the great majority of mRNAs, usually has a 5' cap and a poly(A) tail.
C) MicroRNAs are produced by germ-line cells only.
D) An miRNA is initially produced as a duplex RNA but in order to work it needs to be converted into a single-strand RNA.