Your project manager asked you for your advice.

The human-centered design process emphasizes iterative development—testing and refining designs through multiple cycles. In the scenario, the project manager interviewed users and evaluated a prototype but did not iterate based on feedback. Skipping iteration likely resulted in unmet user needs. Human-centered design, per ISO 9241-210, includes: understanding context of use, specifying requirements, producing design solutions, and evaluating—repeated iteratively. Hence, option D (“iterate”) is correct.