Final answer:
The persuasive speech proposition about eating dark chocolate because of its antioxidants content is an example of a proposition of fact, as it's based on verifiable evidence.
Step-by-step explanation:
Developing a persuasive speech asserting that your audience should eat dark chocolate because it's been proven to be rich in antioxidants is an example of a speech proposition of fact.
This type of proposition relies on evidence such as statements of fact, statistics, and expert opinion to prove or verify the truthfulness of the assertion that dark chocolate is rich in antioxidants. The goal here is not just to provide information but to convince the audience that they should act upon this information, a common technique in persuasive writing and public speaking.