A. Backup the existing metadata using the ANT Migration Tool. To roll back deployment, deploy again to production using backed up metadata.

B. Backup the existing metadata using ANT Migration Tool. To roll back deployment, manually delete new components and deploy again to production using backed up metadata.

C. Create a sandbox from production to take the backup of existing metadata. To roll back deployment, use destructivechanges.xml to delete new components and then deploy again to production using metadata from this sandbox.

D. Create a sandbox from production to take the backup of existing metadata. To roll back deployment, manually delete new components and then deploy again to production using metadata from this sandbox.