Which of the following statements about regulation of eukaryotic gene expression is incorrect?

a) the presence of a nuclear membrane separating transcription and translation in eukaryotes led to the evolution of additional mechanisms of gene regulation.
b) in eukaryotes, most structural genes are found within operons.
c) eukaryotic mrnas are generally more stable than prokaryotic mrnas.
d) the rate of degradation of mrnas is important in regulation in eukaryotes.
e) posttranslational regulation of histones is unique to eukaryotes.