Link aggregation is a technique that allows multiple network interfaces to act as a single logical interface, increasing the bandwidth and redundancy of the network connection. Link aggregation can improve the performance of the network by balancing the traffic load across multiple links and providing failover in case one link fails. Link aggregation is also known as port trunking, port channeling, or NIC teaming.

A splitter is a device that divides a coaxial cable into two or more branches, allowing multiple devices to share the same cable connection. However, a splitter also reduces the signal strength and quality of the cable, which can affect the performance and reliability of the devices connected to it. A signal power of -97dB is very low and indicates a weak or poor cable signal, which can cause constant disconnections and slow speeds.
The support agent should recommend removing any splitters connected to the line and connecting the coaxial modem directly to the cable outlet. This can help to improve the signal power and quality of the cable, and thus enhance the performance and reliability of the wired devices. Alternatively, the support agent can also suggest using a signal amplifier or booster, which is a device that increases the signal strength and quality of the cable, to compensate for the signal loss caused by the splitter.
The other options are not correct because they are not the best recommendations to troubleshoot the issue. They are:
Switching the devices to wireless. Switching the devices to wireless may not solve the issue, as the wireless connection may also depend on the cable signal and quality. Moreover, switching the devices to wireless may introduce other problems, such as interference, security, or compatibility issues, that can affect the performance and reliability of the devices.
Moving the devices closer to the modem. Moving the devices closer to the modem may not solve the issue, as the problem is not related to the distance between the devices and the modem, but to the signal power and quality of the cable. Moreover, moving the devices closer to the modem may not be feasible or convenient for the user, depending on the layout and setup of the location.
Lowering the network speed. Lowering the network speed may not solve the issue, as the problem is not related to the bandwidth or capacity of the network, but to the signal power and quality of the cable. Moreover, lowering the network speed may degrade the user experience and satisfaction, as the user may not be able to access or use the network services or applications as expected.
Reference
1: Network+ (Plus) Certification | CompTIA IT Certifications
2: What is a Coaxial Splitter? - Definition from Techopedia
3: What is a Signal Amplifier? - Definition from Techopedia

Mismatched duplex settings can cause an increase in CRC errors, which are errors in data transmission that can result in corrupted data. Reference: CompTIA Network+ Certification Study Guide, Chapter 4: Infrastructure.

A basic service set (BSS) is a group of wireless devices that share the same service set identifier (SSID) and communicate with each other through a single access point (AP). A BSS is also known as an infrastructure mode network1.
An extended service set (ESS) is a group of two or more BSSs that are connected by a distribution system (DS), such as a switch or a router. An ESS allows wireless devices to roam between different APs and maintain network connectivity. An ESS is also known as a wireless LAN (WLAN)2.
An independent basic service set (IBSS) is a group of wireless devices that communicate with each other directly without using an AP or a DS. An IBSS is also known as an ad hoc network or a peer-to-peer network3.
MU-MIMO (Multi-User Multiple-Input Multiple-Output) is a technology that allows an AP to transmit data to multiple wireless devices simultaneously using multiple antennas and spatial streams. MU-MIMO can improve the network efficiency and performance by reducing the waiting time and increasing the throughput4.
The scenario described in the question is an example of an IBSS, as the two laptops are connected directly to each other using 802.11ac without an AP. Therefore, the correct answer is C.
Reference:
1: BSS
2: ESS
3: IBSS
4: MU-MIMO

CVE stands for Common Vulnerabilities and Exposures, which is a list of publicly disclosed cybersecurity vulnerabilities that is free to search, use, and incorporate into products and services. CVE provides a standardized identifier and description for each vulnerability, as well as references to related sources of information. CVE helps to track and document various types of known vulnerabilities and facilitates communication and coordination among security professionals.