![\boxed {\boxed {\sf A. \ Uracil}}](/tpl/images/0949/2319/11659.png)
Explanation:
DNA (deoxyribonucleic acid) has two chains of nucleotides that form a double helix that resembles a twisty ladder. The nucleotides are:
Adenine (A) Guanine (G) Cytosine (C) Thymine (T)
RNA (ribonucleic acid) is different. It only has one chain of nucleotides. The bases are also different:
Adenine Guanine Cytosine Uracil (U)
We see that RNA has a different base! It contains uracil instead of thymine. The correct answer must be A. uracil