THYMINE
When dealing with base pairing in DNA...
g pairs with c and c with g.
a pairs with t and t with a.
But when dealing with base pairing involving RNA...
a pairs with u and u with a.
t pairs with a.
Hope this helped, if it did please mark me brainliest!
(I had misread your question before. Uracil couldn't be that base because it's not in DNA, and is in translation.)
