Final answer:
The revision needed is to move the comma to after the word 'fact' in the sentence.
Step-by-step explanation:
The revision needed to correct the sentence is option A. Move the comma to after the word 'fact'.
The sentence should be: 'As a matter of fact, my dog does know the difference between a treat and a vitamin.'
By moving the comma to after 'fact', it separates the introductory phrase 'As a matter of fact' from the main clause, making the sentence clearer and more grammatically correct.
Learn more about Correcting a sentence with a comma