Which of the Following Statements Concerning DNA,RNA,and Their Components Is

Multiple Choice

Which of the following statements concerning DNA,RNA,and their components is (are) not correct?

A) Phosphoric acid has three dissociable OH groups which can also react with alcohols to form phosphoesters.
B) Across the DNA helix,purine bases hydrogen bond only to other purine bases.
C) The two substituted pyrimidines in DNA are cytosine and thymine.
D) both B and C
E) none of the above