Which sentence contains a comma that is correctly placed but unnecesary?

A. I wanted to sleep late, but it was a school day.

B. However, it wasn't worth the effort.

C. We hopped, skipped and jumped in gym class today.

D. Her favorite vegetables are corn, beans, peas, and asparagus.

it would be D. Her favorite vegetables are corn, beans, peas, and asparagus.

D. Her favorite vegetables are corn, beans, peas, and asparagus.

Explanation:

Sentence D contains an 'Oxford comma'; it is a comma used after the penultimate item in a list of three or more items, before the conjunction 'and'.

Not all writers and publishers use the 'Oxford comma' because it is an optional comma. For instance, sentence C has a list of three items, yet it does not use a comma before 'and'.