Answer & Explanation
C) Increase the time between the differential backup and the DBCC SHRINKDATABASE job.
The DBCC SHRINKDATABSE cannot be executed until the previous job step, the differential backup, has been completed. We should increase the time between these two job steps, or even better configure the last job step to run only after the differential backup has been completed.
Note: The DBCC SHRINKDATABASE statement shrinks data files on a per-file basis but shrinks log files as if all the log files existed in one contiguous log pool. The target size for the data and log files cannot be smaller than the minimum size of a file that was specified when the file was originally created, or the last explicit size set with a file size changing operation such as the ALTER DATABASE statement with the MODIFY FILE option or the DBCC SHRINKFILE statement.