Answer:
D
Step-by-step explanation:
Well, A has to be an answer because, think of this example;
"But, he did have a great time at the beach afterall"
B- to separate 3 or more words. This one too because i could say;
"Cats and dogs"
BUT,
"Marley had dogs, cats, and birds."
C- When using introductory phrases like;
"Furthermore, cats are better because..."
So its D because all of them are a correct way to use commas.