Link Aggregation is the combining of multiple network connections in parallel by any of several methods, in order to increase throughput.

The question asks about the least amount of equipment to segment two departments that have cables terminating in the same room.
Segmentation is the process of dividing a network into smaller logical units for security, performance, or management purposes.
One way to segment a network is by using VLANs (virtual LANs), which are logical groups of devices that share the same broadcast domain, regardless of their physical location or connection.
VLANs can be configured on switches that support Layer 2 or Layer 3 functionality. Layer 2 switches operate at the data link layer and forward frames based on MAC addresses. Layer 3 switches operate at the network layer and forward packets based on IP addresses.
A Layer 3 switch can perform both Layer 2 and Layer 3 functions, and can also route traffic between different VLANs without the need for an external router. This makes it a versatile and efficient device for network segmentation.
Therefore, the answer is C, a Layer 3 switch, as it can segment two departments with the least amount of equipment.
Reference:
CompTIA Network+ N10-008 Study Guide, Chapter 2: Network Devices and Technologies, Section 2.1: Network Devices, Pages 74-75 Professor Messer's CompTIA N10-008 Network+ Course, Video 2.1: Network Devices, Part 1 Network + N10-008 practice exam, Question 977, Answer C, Explanation

A DHCP scope is a range of IP addresses that a DHCP server can assign to clients on a network.
If the DHCP scope is fully utilized, it means that there are no more available IP addresses to assign to new clients.
This can cause some internal users who cannot connect to network resources, as they will not have a valid IP address to communicate with other devices on the network.
The users may have been able to connect last week, but not today, because their previous IP address lease may have expired and they could not renew it due to the lack of available IP addresses.
The other options are less likely to cause the issue, because:
B . Electrical interference can affect the quality of the wired network, but it will not prevent users from obtaining an IP address.
C . A captive portal is a web page that requires users to authenticate or accept terms of service before accessing the network. If the captive portal is down, it may prevent users from accessing the internet, but not the internal network resources.
D . SNMP traps are messages sent by SNMP agents to SNMP managers to notify them of events or conditions on the network. They do not affect the connectivity of the users, unless they trigger some network management actions that block or limit the traffic.
E . The packet counter on the router interface is a metric that shows how many packets have been sent or received on that interface. It does not indicate any problem with the network connectivity, unless it reaches a threshold that causes the interface to drop packets.
Reference:
1: CompTIA Network+ N10-008 Study Guide, Chapter 3: IP Addressing, page 104
2: Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 3.2: DHCP, page 27
3: CompTIA Network+ N10-008 Study Guide, Chapter 2: Network Cabling and Topologies, page 69
4: Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 4.1: Network Services, page 36
5: CompTIA Network+ N10-008 Study Guide, Chapter 7: Network Management, page 276
6: Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 7.1: Network Monitoring, page 66

A client-to-site VPN and a split-tunnel VPN are the best options for designing a secure remote access scheme that meets the given requirements. A client-to-site VPN allows users at multiple locations to access corporate resources over the internet by creating a secure tunnel between their devices and a VPN concentrator on the corporate network1. A split-tunnel VPN allows the on-premises equipment to handle only the traffic that is destined for the corporate resources, while the non-corporate traffic is routed directly to the internet without passing through the VPN tunnel2. This reduces the bandwidth and processing load on the corporate network and improves the performance of the remote access.
Reference:
Remote Access - N10-008 CompTIA Network+ : 4.41
comptia Network+ : Remote Access Methods And Network Monitoring2