An administrator needs to restore a source database from a snapshot.

 The correct answer is A because NDB handles the database restore operation by copying the specific database files from the snapshot volume to the source volume, without affecting the other databases that share the same source volume. NDB uses a copy-on-write mechanism to create snapshots and clones, which means that only the changes made to the database files are stored in the snapshot or clone volume, while the original files are kept in the source volume. Therefore, when restoring a source database from a snapshot, NDB only needs to copy the specific database files that have been modified since the snapshot was taken, and overwrite them on the source volume. The other options are not correct because they either cause data loss or unnecessary data transfer. Option B is not correct because replacing the source volume with specific db disks would erase the other databases that share the same source volume, which is not desirable. Option C is not correct because replacing the source volume with the snapshot volume would also erase the other databases that share the same source volume, as well as any changes made to the source database after the snapshot was taken, which is not desirable. Option D is not correct because copying all database files to the source volume would be inefficient and unnecessary, as only the modified files need to be copied, and the other files are already present on the source volume. References: Nutanix Database Management & Automation (NDMA) course, Nutanix Certified Professional - Database Automation (NCP-DB) certification, Nutanix NCP-DB Certification Exam Syllabus and Study Guide, [Nutanix Support & Insights]