ACT Conventions of Standard English Practice Test

Separating items in a list with punctuation keeps the meaning clear, especially when there are three or more items. The sentence that lists three distinct items uses a comma after each item, including the final one before the conjunction: apples, bananas, and cherries. This serial (or Oxford) comma before “and” helps prevent ambiguity and signals clearly that there are three separate things.

The other sentences fail because they don’t consistently separate the items. One has no commas at all, so it’s hard to tell where each item ends. Another places a comma after the first item but not after the second, which breaks the pattern of listing items. The last one puts the comma before the and but misses the comma that should come after the first item, making the list feel off.