This is the most likely cause of the issue because firewall rules can block or allow traffic based on source, destination, port, protocol, or other criteria. If the firewall rules are not configured properly, they can prevent remote users from accessing the cloud application server, while allowing on-site users to access it.References:
https://docs.microsoft.com/en-us/azure/virtual-network/security-overview

Signal blocking is a technique that prevents or reduces the transmission of electromagnetic signals from a building to the outside. Signal blocking can be achieved by using materials that absorb, reflect, or scatter the signals, such as metal, concrete, or mesh. Signal blocking can protect the data center from eavesdropping, interference, or jamming by unauthorized parties1.
Camouflage is a technique that disguises or conceals the appearance of a building to make it less noticeable or identifiable from the outside. Camouflage can be achieved by using colors, patterns, shapes, or vegetation that blend in with the surrounding environment. Camouflage can protect the data center from detection, reconnaissance, or targeting by hostile parties

The administrator is attempting to establish the recovery point objective (RPO) by determining how frequently backups need to be performed on an application server. RPO is a metric that defines how much data can be lost or how far back in time a recovery can go in case of a disaster or disruption, based on the business requirements and impact analysis of an organization or system. RPO is measured by the time interval between backups or snapshots of data, such as hourly, daily, weekly, etc., depending on how critical or sensitive the data is and how often it changes or updates. References: [CompTIA Server+ Certification Exam Objectives], Domain 5.0: Security, Objective 5.3: Given a scenario, explain methods and techniques to secure data.

The administrator should close ports 21 and 23 to secure the server properly. Port 21 is used for FTP (File Transfer Protocol), which is an unsecure protocol that allows file transfer between a client and a server over a network connection. FTP does not encrypt the data or the credentials that are transmitted, making them vulnerable to interception or modification by attackers. Port 23 is used for Telnet, which is an unsecure protocol that allows remote login and command execution over a network connection using a CLI. Telnet does not encrypt the data or the credentials that are transmitted, making them vulnerable to interception or modification by attackers.
Reference:
https://www.csoonline.com/article/3191531/securing-risky-network-ports.html

Asnapshotis a point-in-time image of a system's state that can be created while the system is running, without interrupting operations. Snapshots can be used to restore the entire system to the exact state at the time of the snapshot. They are commonly used in virtualized environments and allow administrators to roll back to a previous state if needed.
* Snapshot (Answer A):Captures the entire system's state and can be taken without downtime.
* Archive (Option B):Refers to long-term storage, not necessarily something that supports live backups.
* Open file (Option C):Refers to a method that handles open files during backup but doesn't provide full system restoration capabilities.
* Differential (Option D):Backs up only the data changed since the last full backup but still requires a full backup for complete system restoration.
CompTIA Server+ Reference:This topic is related toSK0-005 Objective 4.1: Explain backup and recovery methods.