Explanation:

The Dynamic Host Configuration Protocol (DHCP) server is a network service that automatically assigns IP addresses and other related network configuration information to client devices. It plays a crucial role in managing the network and ensuring efficient communication between devices. The correct answer to the given question is option 'D' - all of the mentioned. Let's understand each point in detail:

Maintains a database of available IP addresses:
The DHCP server maintains a database or pool of available IP addresses that it can assign to client devices. This ensures that IP addresses are not duplicated and allows for efficient management of the network. When a client requests an IP address, the DHCP server checks its database to find an available address to assign.

Maintains information about client configuration parameters:
In addition to IP addresses, the DHCP server also maintains information about other network configuration parameters for client devices. These parameters include subnet masks, default gateways, DNS server addresses, and other options required for proper network connectivity. By storing this information, the DHCP server can provide clients with the necessary configuration to connect to the network.

Grants an IP address when receives a request from a client:
When a client device connects to the network, it sends a DHCP request to the DHCP server, requesting an IP address and other configuration parameters. The DHCP server receives this request and checks its database for an available IP address. If an address is available, the server grants it to the client, along with the necessary configuration information. This process is known as DHCP lease allocation.

All of the mentioned:
Therefore, the DHCP server performs all of the mentioned tasks - maintaining a database of available IP addresses, storing client configuration parameters, and granting IP addresses when receiving requests from clients. This comprehensive functionality ensures efficient management and allocation of IP addresses in a network environment.