Regarding exons, which, if any, of the following statements is correct?
(A)Some exons in protein-coding genes consist of noncoding DNA. (B)The first exon of a protein-coding gene always contains the translational start site. (C)The last exon of a protein-coding gene always contains the normal termination codon. (D)A coding exon is always translated in just one of the three possible forward reading frames.
A