a. A snapshot is a point-in-time copy of data that does not depend on other files. A differential backup backs up files that have changed since the last full backup and does not require any other file to restore data.

Explanation
A public cloud is a cloud model that provides shared resources and services over the internet to multiple users or organizations. The cloud provider owns and manages the infrastructure and charges users based on their usage or subscription. A public cloud can offer scalability, flexibility, and cost-efficiency for users who need access to various applications and data without investing in their own hardware or software. Verified References: [Public cloud], [Cloud model]

After an update, if a core service fails to start, potential causes include dependencies, authentication, or incomplete updates:
* The server requires another reboot to complete the rollback (A): Some updates require multiple reboots, but if rolling back did not resolve the issue, a missing dependency is more likely.
* The administrator is not authorized to run the service (B): If the administrator previously had access and the update broke the service, it is likely due to software conflicts rather than permissions.
* The server requires further updates of other software components (C): Many services rely on dependent libraries, drivers, or patches. If an update replaces or removes a necessary component, the service may fail until additional updates are applied.
* The account used to run the service has expired (D): Expired accounts usually cause authentication failures but not outright service crashes unless explicitly required for the update process.
Since rolling back the update did not fix the issue, the most likely reason is that additional updates or dependencies are missing.
Reference: CompTIA Server+ SK0-005 Official Textbook, Chapter 8 - System Maintenance and Troubleshooting

You can run nmap to determine what ports are open and what services are running on them and could even run a -sV to determine version.

JBOD (Just a Bunch Of Disks) is a storage configuration that combines different types and sizes of hard drives into one logical unit without any RAID level or redundancy. It allows users to see all the drives within the unit as one large storage space. JBOD can utilize all the available capacity of the drives but does not provide any performance or fault tolerance benefits. Verified References: [JBOD], [RAID]