Question

which base is found only in dna?
adenine
guanine
cytosine
thymine

Explanation:

DNA has four nitrogen - containing bases: adenine (A), guanine (G), cytosine (C), and thymine (T). RNA has adenine (A), guanine (G), cytosine (C), and uracil (U). So, thymine is unique to DNA.

Answer:

thymine