Making a bandwagon appeal in a persuasive speech is an example of using unsubstantiated opinion.
Explanation: The bandwagon appeal is a fallacy because it argues in favor of something that is popular, and it is considered an unsubstantiated opinion because "everyone is doing it" is not valid evidence.
Cultural context, central ideas, and language are important to consider when identifying the purpose of a speech.
Explanation: Cultural context is the beliefs, behavior, and way of life that pertains to a specific cultural and is a key elements to speeches - it affects how you see the audience, and vise versa. Central idea is the main idea expressed in a speech, and language sets the tone of the speech.