C) is the correct option
Step-by-step explanation:
Splicing is the post transcriptional modification of pre mRNA which occurs in nucleus just after transcription but before the RNA moves to the cytoplasm
In RNA splicing non coding regions of pre mRNA called introns are removed and coding regions called exons are religated
Removal of every intron require two transesterification reaction:
First transesterification reaction displaces exon from intron with 3' OH group
Second transesterification reaction always catalysed by 3'OH group of displaced exon at 3'splice site