A divide-and-conquer approach is a troubleshooting method that involves breaking a complex problem into smaller and more manageable parts, and then testing each part to isolate the cause of the problem. In this scenario, the technician is using a divide-and-conquer approach by pinging the default gateway and DNS server of the workstation, which are two possible sources of connectivity issues. By pinging these devices, the technician can determine if the problem is related to the local network or the external network.

The correct tool for verifying existing network connections on a server is C. Netstat. Netstat (network statistics) displays active network connections, routing tables, interface statistics, masquerade connections, and multicast memberships.
Tracert: Tracert (traceroute) is used to trace the route taken by packets from the source to the destination. It helps identify the path and latency between routers.
Ipconfig: Ipconfig is used to view and manage IP configuration settings on a local machine (such as IP address, subnet mask, default gateway, etc.). It does not provide information about existing connections.
Netstat: Netstat displays active network connections, including listening ports, established connections, and associated processes. It's useful for troubleshooting and monitoring network activity.
Nslookup: Nslookup is used for DNS (Domain Name System) queries to resolve domain names to IP addresses. It does not provide information about existing connections.
Reference:
CompTIA Network+ Certification Exam Objectives

See the solution configuration below in Explanation
Explanation:
Network Health:
WAN 2 appears to have a lower average latency and loss percentage, which would make it the preferred WAN station for VoIP traffic. VoIP traffic requires low latency and packet loss to ensure good voice quality and reliability. WAN 1 seems to have higher RAM and processor usage, which could also affect the performance of VoIP traffic.
Here's the summary of the key metrics for WAN 1 and WAN 2 from the image provided:
WAN 1:
Uplink Speed: 10G
Total Usage: 26.969GB Up / 1.748GB Down
Average Throughput: 353MBps Up / 23.42MBps Down
Loss: 2.51%
Average Latency: 24ms
Jitter: 9.5ms
WAN 2:
Uplink Speed: 1G
Total Usage: 930GB Up / 138GB Down
Average Throughput: 12.21MBps Up / 1.82MBps Down
Loss: 0.01%
Average Latency: 11ms
Jitter: 3.9ms
For VoIP traffic, low latency and jitter are particularly important to ensure voice quality. While WAN 1 has higher bandwidth and throughput, it also has higher latency and jitter compared to WAN 2. However, WAN 2 has much lower loss, lower latency, and lower jitter, which are more favorable for VoIP traffic that is sensitive to delays and variation in packet arrival times.
Given this information, WAN 2 would generally be preferred for VoIP traffic due to its lower latency, lower jitter, and significantly lower loss percentage, despite its lower bandwidth compared to WAN 1. The high bandwidth of WAN 1 may be more suitable for other types of traffic that are less sensitive to latency and jitter, such as bulk data transfers.

Device Monitoring:
the device that is experiencing connectivity issues is the APP Server or Router 1, which has a status of Down. This means that the server is not responding to network requests or sending any dat a. You may want to check the physical connection, power supply, and configuration of the APP Server to troubleshoot the problem.

BGP stands for Border Gateway Protocol, and it is the standard protocol for exchanging routing information between different autonomous systems (AS) on the internet12. An AS is a network or a group of networks under a single administrative control, such as an ISP or a large enterprise12.
BGP is an Exterior Gateway Protocol (EGP), which means it is used to communicate with routers outside the local network or AS12. BGP allows each AS to advertise its own routes and policies to other ASes, and to learn the best routes to reach any destination on the internet12.
BGP is generally used by major ISPs for handling large-scale internet traffic because it is highly scalable, flexible, and reliable12. BGP can handle millions of routes and thousands of ASes, and it can support various routing policies and preferences12. BGP also has mechanisms to detect and avoid routing loops, and to recover from network failures12.
The other options are not suitable for handling large-scale internet traffic across different ASes. RIP (Routing Information Protocol) and EIGRP (Enhanced Interior Gateway Routing Protocol) are both Distance Vector protocols, which means they use the number of hops as the metric to find the best route34. They are also Interior Gateway Protocols (IGP), which means they are used to communicate with routers within the same network or AS34. RIP and EIGRP are not scalable or flexible enough to handle the complexity and diversity of the internet34. OSPF (Open Shortest Path First) is a Link State protocol, which means it uses the speed and cost of the links as the metric to find the best route5. It is also an IGP, which means it is used to communicate with routers within the same network or AS5. OSPF is more scalable and flexible than RIP and EIGRP, but it still has limitations in handling large-scale internet traffic across different ASes5. Reference:
1: CompTIA Network+ N10-008 Certification Study Guide, Chapter 3: Routing, Section 3.4: BGP6
2: Professor Messer's CompTIA N10-008 Network+ Course Notes, Page 18: BGP7
3: CompTIA Network+ N10-008 Certification Study Guide, Chapter 3: Routing, Section 3.2: RIP and EIGRP6
4: Professor Messer's CompTIA N10-008 Network+ Course Notes, Page 16: RIP and EIGRP7
5: CompTIA Network+ N10-008 Certification Study Guide, Chapter 3: Routing, Section 3.3: OSPF6
6: CompTIA Network+ N10-008 Certification Study Guide2
7: Professor Messer's CompTIA Network+ N10-008 Training Course5

netstat is a command-line tool that displays network connections, routing tables, interface statistics, and more. It can help the technician identify which processes or applications are using the network bandwidth on the user's computer. netstat can also show the current bandwidth usage in bytes per second for each network interface.
Reference
netstat - Wikipedia provides an overview of the netstat tool and its features.
How to get current bandwidth usage from command line using built-in Linux tools? - Super User explains how to use netstat and other tools to monitor bandwidth usage on Linux systems.
Get network utilization from command line - Super User shows how to use typeperf and other tools to monitor bandwidth usage on Windows systems.