Question

When separating items in a list, a writer should

end the list with a colon.
separate the items with colons.
add a comma after the “and” before the last item.
add a comma before the “and” before the last item.

Answer 1

add a comma before the “and” before the last item.

(This is the serial/Oxford comma — e.g., "apples, oranges, and bananas.")