After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?1. A translation stop codon is added at the 3' end of the pre-mRNA.2. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA.3. A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA.4. Coding sequences called exons are spliced out by ribosomes.5. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.