Which document identifies activities to give confidence to stakeholders about how programme risks are managed?

Comprehensive and Detailed Explanation From Exact Extract:

The assurance plan outlines the activities that provide stakeholders with confidence that risks are identified, evaluated, and managed properly. It supports the “assurance” theme and includes information about the timing, scope, and responsibilities for assurance activities.

MSP Foundation, 5th Edition explains:

“The assurance plan includes the schedule and scope of assurance activities to ensure stakeholders are confident that risk and controls are effectively managed.”

Thus, A is correct.