We have deoxy guanosine, five prime triphosphate. We have deoxy pyridine, five prime triphosphate, and we have the thymidine, five prime triphosphate. So for the DNA polymerase to actually build and extend the DNA polynucleotide chain, it has to have those four nucleotides swimming around in that solution. Without those nucleotides, it will not be able to build our structure in the same way that we cannot build a building without the bricks, the building blocks. Let's move on to B. So, DNA polymerase requires a template DNA strand and that's because it's the template DNA strand that essentially provides the blueprint, the instructions to build that replicated strand of DNA.