<prompt> Which of the following are Pyrimidine bases?Adenine and GuanineGuanine and CytosineCytosine and AdenineThymine and Cytosine  <response>: In DNA and RNA, Pyrimidine bases form hydrogen bonds with their complementary purines. Thus, in DNA, the purines adenine A and guanine G pair up with the pyrimidines thymine T and cytosine C, respectively. In RNA, the complement of adenine A is uracil U instead of thymine T, so the pairs that form are adenine: uracil and guanine: cytosine. Ref: Rodwell V.W. 2011. Chapter 32. Nucleotides. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell Eds, Harpers Illustrated Biochemistry, 29e 