Answer: The prefix and word combination that correctly uses a hyphen is "Ex-husband".
Explanation: Punctuation rules state that a hyphen should always be used when the prefix "ex" is part of a word. In that way, the prefix and word combination that correctly uses a hyphen is "ex-husband". On the other hand, although the other words provided also contain a prefix, the hyphen should not be added because its absence does not cause a confusion with another word.
