The cDNA for a eukaryotic gene B is 900 nucleotide pairs long.A cDNA clone is used to isolate a genomic clone of gene B,and the gene is sequenced.From start to stop codon,the gene is found to be 1800 nucleotide pairs long.The most probable reason for the discrepancy is that:
A)the mRNA broke during cDNA synthesis. B)the gene is present as a tandem duplication. C)the gene has 900 nucleotide pairs of introns. D)the genomic clone is not really gene B,just a related gene. E)there was a sequencing error.