Which statement correctly describes the roles of 5' capping, splicing, and 3' poly(A) tail in eukaryotic mRNA processing?

• A. 5' capping marks the end of transcription; splicing adds introns; polyadenylation begins translation.
• B. 5' capping stabilizes mRNA without affecting export; splicing removes exons; polyadenylation shortens mRNA.
• C. 5' capping stabilizes mRNA and aids export and translation; splicing removes introns and joins exons; 3' poly(A) tail stabilizes mRNA and enhances translation.
• D. 5' capping occurs after transcription; splicing occurs in the cytoplasm; polyadenylation occurs before transcription start.

Answer: (C)

The key idea is how eukaryotic mRNA is prepared for use in the cytoplasm: a 5' cap is added to help stability, export, and translation initiation; introns are removed and exons joined by splicing; and a 3' poly(A) tail is added to protect the message and aid translation. The correct description captures all of these roles together: the 5' cap stabilizes the mRNA and supports export and translation; splicing removes introns and joins exons; the 3' poly(A) tail stabilizes the mRNA and enhances translation. The other options mix up where these processes occur or what they do—for example, capping occurs during transcription and influences export and translation (not just marks transcription’s end), splicing removes introns (not exons), and the poly(A) tail does not shorten mRNA but helps stabilize it and improve translation.