The suggested answer is A, C, D.
In the planning phase of the Software Assurance Acquisition process, several vital activities are undertaken to ensure that software requirements, strategies, and evaluation criteria are adequately prepared. First, developing software requirements is crucial as it ensures the acquired software meets all functional and security specifications. Second, creating an acquisition strategy is essential as it outlines the approach for procuring software and addresses potential risks. Lastly, developing evaluation criteria and an evaluation plan allows stakeholders to establish a clear framework for assessing the proposals and capabilities of potential vendors. Implementing change control procedures is not part of the planning phase but rather associated with the monitoring and acceptance phase to handle deviations during and after deployment.