Post-Transcriptional modification of RNA

Which of the following is not a post-transcriptional modification of RNA?

A. Splicing 
B. 5- capping
C. 3'-poly adenylation 
D. Glycosylation

Answer. D. Glycosylation

Glycosylation has not been mentioned as a post-transitional modification of RNA.

5' - capping: Is required both for efficient translation initiation and protection of 5' - end of MRNA from attack by 5'-3' exonucleases.

3' - poly adenylatlon: Added to 3'-end of mRNA molecules in a post transcriptional processing step. This appears to protect the 3'-end of mRNA from 3' - 5' exo-nuclease attack.