The enzyme poly-A polymerase is responsible for adding 3' poly-A tails to eukaryotic mRNAs. This enzyme...

A) cuts the mRNA after recognition of the cleavage/polyadenylation signal by CstF and CPSF proteins.
B) polymerizes the tail using an RNA template that is part of the enzyme.
C) is extremely processive.
D) normally adds about 1000 A nucleotides to the mRNA.
E) uses ATP as a substrate.