The correct option is A A GTP cap and a poly A tail are added to protect the mRNA as it leaves the nucleus.
Post-transcriptional modification of hnRNA in eukaryotes includes three events. Splicing is the removal of introns from the primary transcript and ligation of exons to form a continuous sequence specifying a functional polypeptide. Capping of eukaryotic mRNAs refers to the addition of 7-Methylguanosine to the 5’ end of almost all eukaryotic mRNAs in an unusual 5’,5’- triphosphate linkage where the 5' diphosphate end is attacked by the phosphorus atom of GTP molecule to add guanine residue at the 5’,5’- triphosphate linkage. Tailing refers to cleavage of 3’ end and the addition of 80 to 250 A residues to create a poly(A) tail. Thus, the correct answer is option A.