Answer:
D. All of the choices are correct.
Step-by-step explanation:
In order to keep the audience engaged in a speech, one must ensure that they're using proper language and terms that will be understood by the audience rather than leaving them confused. Rhetorical devices are extremely useful when delivering a speech, because they allow your words and message to be more impactful. While not always necessary, visual aids do help keep audiences more engaged and help better convey the message of the speech. Therefore, all of the choices listed are correct.