Which of the following statements about eukaryotic mRNA processing is not correct?
a. the mRNA transcipt must be exported from the nuleus
b. a 5' cap and a 3' poly(A) tail must be added
c. the introns are removed
d. a 3' cap and a 5' poly(A) tail must be added
e. exons are spliced together to form the mRNA transcript