21.Please select the CORRECT description from the following options related to nucleic acids:
(A) A is mostly base paired with C
(B) Structure of nucleotides are composed of six-member ring sugar, base and phosphate group.
(C) The linkage between nucleotides is phosphodiester bond
(D) Nucleic acids at neutral pH buffer (pH=7) are highly negatively charged
(E) Quantification of DNA is based on absorbance 280nm