The Reverse Transcriptase Enzyme of Retroviruses Includes Between 1 and 10

The reverse transcriptase enzyme of retroviruses includes between 1 and 10 mistakes when it copies the viral genome into DNA.Which of the following explains why?

A) It lacks the 3'-to-5' exonuclease activity found in the cellular DNA polymerase.
B) It lacks the 5'-to-3' exonuclease activity found in the cellular DNA polymerase.
C) It doesn't bind to the cellular proteins involved in proofreading.
D) The virus doesn't produce the proteins involved in proofreading.
E) The production of RNA is inherently more mistake prone than the production of DNA.