The correct answer is (D) Monitor Server.

In a Local Area Network (LAN), the essential hardware components include:

• NIC (Network Interface Card): This is required for connecting devices to the network.
• File Server: This is often used in a LAN to store and manage files, but it's not strictly required for the network itself to function.
• Coaxial Cable: This is a type of cable that can be used for network connections, although modern LANs often use Ethernet cables (twisted pair cables).

However, a Monitor Server is not necessary for the basic operation of a LAN. The monitor is typically used for user interaction, not for networking functionality.