Explanation
A DHCP reservation is a way to assign a specific IP address to a device based on its MAC address, which is a unique identifier for each network interface card (NIC). When the administrator replaced the NIC, the MAC address of the server changed, and the DHCP server no longer recognized it as the same device. Therefore, the DHCP server assigned a different IP address to the server, which was incorrect for the application. To fix this problem, the administrator needs to modify the DHCP reservation to use the new MAC address of the NIC, so that the server can get the proper IP address.
A WWNN (World Wide Node Name) is a unique identifier for a Fibre Channel node, which is a device that can communicate over a Fibre Channel network. A WWNN is not related to DHCP or IP addresses, and it is not used for DHCP reservations. Therefore, options B and D are incorrect.
Updating the local hosts file with the correct IP address (option C) is also incorrect, because it does not solve the problem of getting the correct IP address from the DHCP server. The hosts file is a local file that maps hostnames to IP addresses, and it is used to override DNS queries. However, it does not affect how the DHCP server assigns IP addresses to devices. Moreover, updating the hosts file manually on every device that needs to communicate with the server is not a scalable or efficient solution.
References:
How to reserve IP Address in DHCP Server - Ask Ubuntu
Static IP vs DHCP Reservation - The Tech Journal
How to Configure DHCP Server Reservation in Windows ... - ITIngredients

HIDS (Host Intrusion Detection System): Continuously monitors a system for suspicious activity and logs or raises alerts when potential threats are identified. This proactive approach is crucial for identifying and mitigating threats on a web server exposed to the external network.
Applying OS updates: While essential for maintaining system security, updates address vulnerabilities and may not necessarily identify ongoing threats.
Disabling unused services: Reduces the attack surface by minimizing potential entry points for malicious actors, but doesn't actively identify threats.
Installing anti-malware: Primarily designed to detect and remove malware after infection, not for ongoing threat identification.
Reference:
CompTIA Server+ Objectives (Exam codes SK0-004 or SK0-005): Search for sections on intrusion detection and prevention.

Explanation
After removing the virus from the server, the administrator should perform the following actions to mitigate the issue from reoccurring and to maintain high availability:
Run a vulnerability scanner on the server to identify any other potential weaknesses or exposures that could be exploited by attackers.
Patch the vulnerability that allowed the virus to infect the server in the first place, using the latest updates from the database software vendor or a trusted source.
Update the antivirus software on the server to ensure it has the most recent virus definitions and can detect and prevent future infections. The other options are either unnecessary or counterproductive for this scenario. Repartitioning the hard drive, reformatting the OS, removing the database software, or air gapping the server from the network would cause downtime and data loss, while enabling a host firewall would not prevent a virus infection from within the network. References: CompTIA Server+ Certification Exam Objectives, Domain 5.0: Security, Objective 5.2: Given a scenario involving a security threat/vulnerability/risk, implement appropriate mitigation techniques.

The Common Internet File System (CIFS) is a dialect or an implementation of the SMBs protocol.
Most references will be to SMB, and that is the proper term by today's standards. One of the most common servers on the network are file servers. These devices are designed to store large numbers of files. Workstations access to these files from across the network. Application layer protocols manage file access. The two most common protocols are the Network File System (NFS) and Server Message Blocks (SMB).

Bare Metal OS installed directly on the server hardware
Traditional installation option
Resources not shared among multiple installations
Provides the security, reliability, and performance required by some industries May be more costly than virtualization