Which of the Following Statements About Protein Modifications Is INCORRECT

Which of the following statements about protein modifications is INCORRECT?

A) Addition of one or more sugar molecules results in a fully mature protein called a glycoprotein.
B) Proteins can be modified by reversible addition or subtraction of a phosphate group.
C) Proteins can be modified following the addition of a polyadenylated tail.
D) Phosphorylation or dephosphorylation is a rapid way of activating or inhibiting proteins.
E) Protein modification most often causes a change in conformation and thus a change in function.