The sentence that displays correct subject-verb agreement is: "The people in the audience stand as the show ends."
The other sentences have issues with subject-verb agreement:
- "The dialogue spoken by the actors make the crowd roar with laughter." (Should be "makes")
- "The actors in the play returns to take another bow." (Should be "return")
- "The helpers working behind the stage comes out, too!" (Should be "come")