Final answer:
The best technique for a Scrum Master when Developers consistently under-deliver is to encourage open communication, enabling the team to inspect and adapt their practices.
Step-by-step explanation:
When dealing with Developers who consistently deliver less than they forecast during Sprint Planning in a Scrum framework, it is not advisable to implement strict rules or punish underperformance, as these strategies can demotivate the team and damage trust. Instead, the most effective technique is c) Encouraging open communication. As a Scrum Master, fostering an environment where team members feel comfortable discussing impediments, workload, and process improvements is crucial.
By facilitating regular retrospectives and promoting transparency, the Scrum Master can help the team inspect and adapt their practices. Team members can explore reasons behind the shortfall and collaboratively discover ways to improve their forecasting and execution for future sprints, ensuring a more accurate and achievable commitment.