In RNA, which base replaces thymine?

A) cytosine

B) guanine

C) adenine

D) uracil

Uracil is the answer

RNA is a polymer with a ribose and phosphate backbone and four different bases: adenine, guanine, cytosine, and uracil. The first three are the same as those found in DNA, but in RNA thymine is replaced by uracil as the base complementary to adenine. This base is also a pyrimidine and is very similar to thymine.