Final answer:
The speech by The Lorax fits the Problem Cause Solution persuasive speech model, addressing toxic chemical dumps by advocating for changes in local laws.
Step-by-step explanation:
The persuasive speech model best fitting the description provided by the student is B. Problem Cause Solution. This persuasive speech approach outlines a specific issue, explains the cause of the problem, and then proposes a solution. In the given scenario, The Lorax is identifying the problem of toxic chemical dumps by small business owners, explaining the cause which is improper disposal, and advocating for signing a petition to change local pollution laws to prevent future incidents.