Which base is found in RNA but NOT in DNA? A) adenine B) cytosine C) thymine D) uracil

Its Uracil. Uracil is energetically less expensive to produce than thymine, which may account for its use in RNA. In DNA, however, uracil is readily produced by chemical degradation of cytosine, so having thymine as the normal base makes detection and repair of such incipient mutations more efficient

The DNA nucleotide bases include adenine, cytosine, guanine and thymine. The RNA nucleotide bases include adenine, uracil, guanine and cytostine.