This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following is true about capping of RNA following its synthesis 
Select and explain. 
A. Occurs at 3' end of RNA, B. Occurs in nucleus of cell, C. Specific to MRNA of Prokaryotes, D. S-adenosyl methionine (SAM) acts as methyl donor
D: S-adenosyl methionine (SAM) acts as methyl donor
Answer: D: S-adenosyl methionine (SAM) acts as methyl donor 
Explanation: 7 - Methylguanosine attached to 5' end of RNA is called capping of RNA.
Refer byte "Post transcriptional modification".