The two sentences have different verb tenses, and one of them contains a mistake. Here's the breakdown:
1. "A man was arrested by the police"
* This is correct. It uses the past simple tense, which is appropriate when talking about something that happened and is completed in the past.
2. "A man have been arrested by the police"
* This is incorrect. The subject "a man" is singular, so you should use "has" instead of "have."
* The correct sentence is: "A man has been arrested by the police." This is the present perfect tense, which is used when the action has recently happened or has relevance to the present.
Summary:
* "A man was arrested" (past event, completed).
* "A man has been arrested" (recent event, connected to the present).
Both tenses are appropriate depending on the context, but ensure the verb agrees with the subject.