【单选题】A careful analysis of cellular components discovers short-lived RNA species in which an adenine nucleotide is found with three phosphodiester bonds (linked to the 2’, 3’, and 5’ carbons). This transient structure is formed during which of the following processes?
A、mRNA cap formation B、C、 D、 E、Spl
B、mRNA polyadenylation
C、Transcription of rRNA
D、Transcription of microRNAs
E、Splicing of hnRNA