Answer: The base pair that adenine bonds to is thymine!
Step-by-step explanation:
There are 4 base pairs in a DNA strand, adenine, thymine, guanine, cytosine. Adenine will always base pair with thymine, and guanine will always base pair with cytosine. But in RNA, thymine base pairs don't exist, so they will be replaced with uracil. And uracil will be paired with adenine, only in RNA.
A way you can remember these base pairs are; Apples in a Tree ( Adenine + Thymine ), and Cars in a Garage ( Cytosine + Guanine)