39.DNA 複製過程中,下列何種酵素具有校對(proofreading)DNA 序列正確性的功能?(A)引子酶(primase)(B)拓撲異構酶(topoisomerase)(C)5'→3'外切酶 (5'→3' exonuclease)(D)3'→5'外切酶 (3'→5' exonuclease)