DNA polymerase III can only add nucleotides to an existing chain .so __ is required. a. a DNA primer b. DNA polymerase I c. helicase d. an RNA primer

## Step 1<br />The problem is about the process of DNA replication, specifically the role of DNA polymerase III. DNA polymerase III is an enzyme that adds nucleotides to an existing chain during DNA replication.<br /><br />## Step 2<br />However, DNA polymerase III cannot initiate the replication process on its own. It requires a primer to start the replication process.<br /><br />## Step 3<br />The primer is a short strand of RNA that serves as a starting point for DNA synthesis. This primer is laid down by another enzyme called primase.<br /><br />## Step 4<br />The primer is not a DNA primer, but an RNA primer. Therefore, the correct answer is "d. an RNA primer".