Final answer:
Repetition of key words and phrases and the use of descriptive diction are effective rhetorical devices as they emphasize important points and engage the audience's senses and emotions, making the argument more compelling.
Step-by-step explanation:
One effective rhetorical device in a speech is the use of repetition. This device contributes to the quality of the argument by emphasizing key points, creating a rhythm that enhances the speaker's message, and making the speech more memorable for the audience. For example, the repeated use of a phrase can underscore its significance and persuade the audience of its importance. An instance of effective word choice could be the strategic repetition of a term that is central to the speaker's argument, such as 'freedom' in a speech about civil rights, which would evoke strong emotional responses and anchor the entire narrative around this pivotal concept.
Descriptive diction also plays a vital role in the quality of an argument. By choosing words that are vivid and carry connotations beyond their literal meaning, a speaker can paint a compelling picture that appeals to the senses and emotions of the audience. This sensory detail helps to immerse the listeners and can make the argument more impactful and convincing.