Although DNA Replication of One Cell Involves Billions of Nucleotides,why

Although DNA replication of one cell involves billions of nucleotides,why is this process so accurate?

A) DNA primers can replace any mistakes in base-pairing
B) RNA polymerase corrects any mistakes before doing RNA transcription
C) Unwinding the double helix would remove any mistakes in base-pairing.
D) DNA polymerase proofreads and corrects mistakes in base-pairing.
E) Semiconservative replication means that the process is very careful and conservativE.