A) Most cells contain 5 to 10 times more RNA than DNA. B) Ribonucleotides have a number of different metabolic roles. C) The only role of deoxyribonucleotides is as constituents of DNA. D) The electrons for reduction of ribonucleotides to the corresponding deoxyribonucleotides ultimately come from NADPH. E) dTTP can only be synthesized from dCDP.