Universal Containers is validating an outbound change set from the Developer Sandbox to the production...

A and D are the correct answers, as they are the locking behaviors that will occur during a deployment. A is correct, as the production org will be locked and administrators cannot modify metadata during this time, to prevent any conflicts or inconsistencies in the deployment. D is correct, as the production org will be locked and users will still be able to read/write data to the org, to minimize the impact on the business operations and user experience. B is incorrect, as the sandbox org will not be locked and administrators can still modify metadata, as the sandbox org is not the target of the deployment. C is incorrect, as the production org will not be locked and users can only read data during this time, as this would disrupt the business operations and user experience. You can learn more about the locking behaviors in the [Deploy Changes with Change Sets] unit on Trailhead.