During DNA replication two nucleobases form a pair.
Explanation:
In the four-step process of DNA replication, the second step of 'Primer Binding' consists of a comparatively simple operation of the base pairing.
In this operation, two nucleobases bond together to form a pair with the help of hydrogen bonds.
According to the Chargaff's rules, during the operation of base pairing, the guanine in the strand bonds with the cytosine and the adenine in the strand bonds with the thymine.