During DNA replication, which nucleotide will bind to an A nucleotide in the original or parental DNA strand?
Nucleotide one with T base.
In DNA Adenine(A) pairs up with its complementary base Thymine(T).
So during the replication DNA polymerase ( an enzyme ) makes sure that to the base A of parental nucleotide, the nucleotide with base T binds.
If you are getting confused with Uracil (base U), this base only occurs in RNA instead of base T and you do not have to consider it during DNA replication.