So, in a RNA strand, there are nucleotides. Specific ones are always paired with specific other ones.
Adenine and Uracil are paired, and Guanine and Cytosine.
So basically, whenever you see a c, pair it with a G, and the same thing the other way around, and whenever you see an A, pair it with a U. In this case, the T's that have already been placed have to be paired with an A.
