Question

the bases of rna are the same as those of dna with the exception that rna contains
multiple choice
uracil instead of thymine.
cysteine instead of cytosine
cytosine instead of guanine
uracil instead of adenine

Explanation:

DNA has four nitrogen - containing bases: adenine (A), thymine (T), cytosine (C), and guanine (G). RNA also has four bases, but instead of thymine, it has uracil (U). Cysteine is an amino acid, not a nitrogen - containing base. And the other options about base substitutions (cytosine instead of guanine, uracil instead of adenine) are incorrect as per the known composition of RNA and DNA bases.

Answer:

uracil instead of thymine.