Why Does E

Why does E. coli need both DNA polymerse III and DNA polymerase I?

A) DNA polymerase III lacks the 5ʹ → 3ʹ exonuclease activity needed to remove RNA primers.
B) Each polymerase is specific for only one strand of DNA. DNA polymerase III acts only on the leading strand, and DNA polymerase I acts only on the lagging strand.
C) DNA polymerase I is needed to join the Okazaki fragments.
D) The DNA replication is bidirectional; one polymerase is used for each direction.
E) Only DNA polymerase I has proofreading ability.