52. mRNA is a single-stranded RNA that corresponds to the sequence of a gene； meanwhile, mRNA is read by a ribosome in the process of protein synthesis. Which of the following statement is incorrect for mRNA and its role on RNA processing? (A) mRNA is derived from its upstreamed precursor hnRNA. (B) Caps are regularly observed on the 5'-end of mRNA with unmodified pppA and pppT structure. (C) Poly A tails are polymers of 200 to 300 adenylated residues linked with phosphodiester bonds. (D) All hnRNA introns have a guanine-uracil sequence on the 5' border of their intron/exon junctions. (E) Polyadenylation assists stabilize mRNA.