The statement that best explains why the final sentence is effective is C. It asks the audience to play a role in solving a problem.
The final sentence, "But by supporting this bill, you can help make history by ensuring that no child goes to bed hungry," explicitly calls the audience to action, inviting them to be part of the solution by supporting the bill. This direct appeal to the audience's sense of responsibility and their potential impact on a significant issue makes the sentence effective in rallying support and prompting action.