Which of the following is NOT true of a cDNA clone?

A)cDNAs are generally copies of mRNA from expressed genes.
B)Reverse transcriptase activity is required for cDNA cloning.
C)cDNA clones lack exons,as introns are spliced together before cloning.
D)cDNAs are typically smaller than the chromosomal sequence for a particular gene.
E)cDNAs can be fused to a promoter to enable expression of the encoded gene.