The participants did not agree ______ the agenda presented:

With is the correct answer. The phrase agree with is used when expressing the same opinion as someone or when accepting an idea, opinion, or proposal.

• With is correct because the participants did not support or approve the agenda presented.
• For is incorrect because agree for is not a correct English expression in this context.
• About is incorrect because agree about is used when people share the same opinion on a topic, not with an object like an agenda.
• To is incorrect because agree to means to consent to a proposal or request. The natural expression here is agree with the agenda.