So there are three things that DNA polymerase needs. It needs the building blocks, the deoxy nucleuside, triphosphate molecules, and we have four different types. It actually needs that blueprint and that's the template DNA strand that exists in that double helical structure of DNA found inside our nuclei, C. It also needs a primer because the primer must exist for us to extend and build that phosphodiaester bond as we'll see in just a moment. It also actually needs magnesium ions because these magnesium ions essentially increase the efficiency of these DNA polymerase molecules. And we'll discuss that in much more detail when we'll discuss the DNA replication process. Now D, so D is more of a fact about DNA polymerase molecules.