Final answer:
The type of proposal argument that the question 'What should be done to encourage recycling on campus?' represents is a policy proposal.
Step-by-step explanation:
The type of proposal argument that the question 'What should be done to encourage recycling on campus?' represents is a) Policy proposal. This is because the question is seeking a solution or action that can be implemented to address the problem of recycling on campus. A policy proposal suggests a course of action that should be taken to bring about the desired change.