Final answer:
DNA polymerase III is highly processive because it has a high affinity for the template DNA strand and can remain bound to it for long periods of time without dissociating. It also has proofreading activity to correct errors in replication.
Step-by-step explanation:
DNA polymerase III is highly processive because it has a high affinity for the template DNA strand and can remain bound to it for long periods of time without dissociating. This allows DNA polymerase III to continuously synthesize the new DNA strand during replication without frequently falling off the template. Additionally, DNA polymerase III has a proofreading activity, called exonuclease activity, that allows it to correct errors that occur during replication.