Which three techniques would be most helpful in this situation?

The three techniques which are most beneficial here are as follows:

1. Prioritize the list and work on them in order.
2. Alert management to the impediments and their impact.
3. Consult with the Development Team

So, the Scrum master should take care of these things whilekeeping a list of open impediments.

Other than these techniques, all will be beneficial for product and project manager.

• Prioritize the list and work on them in order.
• Alert management to the impediments and their impact.
• Consult with the Development Team.