Final answer:
The project manager should adopt test automation tools to address the root cause of the prolonged test work in the last three agile iterations.
Step-by-step explanation:
The project manager should plan to adopt test automation tools to address the root cause of the increasingly prolonged test work in the last three agile iterations. Test automation tools can help streamline the testing process, reduce manual effort, and increase efficiency. By automating tests, the project team can identify and rectify any issues more quickly, enabling faster feedback and shorter testing cycles.