An instructional method that does not encourage adult participation is:

The instructional method that does not encourage adult participation is the lecture. Lectures typically involve a one-way communication style where an instructor delivers information while participants listen, absorbing content without much interaction or engagement. This format can limit opportunities for adults to ask questions or contribute to the discussion, which is essential in adult learning principles that emphasize collaboration and experience sharing.

In contrast, options like role play, skill practice, and problem-solving discussions actively involve participants, encouraging them to engage with the material, practice new skills, and collaborate with peers to solve problems. These methods align well with adult learning theories that advocate for active participation and experiential learning as ways to enhance comprehension and retention.