Which statement is NOT true of the mRNA for calcitonin?

A) Exons are used for polypeptide synthesis.
B) Introns are complementary to their adjacent exons and will form hybrids with them.
C) The mature mRNA is substantially shorter than the corresponding region on the DNA.
D) The mRNA is originally synthesized in the nucleus, but ends up in the cytoplasm.
E) The splicing that yields a mature mRNA occurs at very specific sites in the RNA primary transcript.