Answer:
A. DNA polymerase
Explanation:
DNA polymerases (I,II,III) proofread the DNA, which helps to catch errors. Errors can be fatal to expression, creating misformed proteins or unclear information, so this is necessary.
Fun facts - the coronavirus is a retrovirus, so it doesn't proofread. That makes it much harder to find a vaccine, because it can generate new strains by the very fact of not proofreading.
