When high-bandwidth services like videoconferencing are introduced, two primary factors may degrade performance:

Incorrect QoS Settings (E):QoS (Quality of Service) is used to prioritize traffic. If not configured correctly, critical services like video may not get the necessary bandwidth and prioritization.

Network Congestion (F):Video services consume large amounts of data. If the network doesn’t have sufficient bandwidth or is not segmented properly, congestion will slow down all services.

DNS misconfiguration (A) would affect name resolution, not bandwidth.

Malware (C) could degrade performance, but is not tied to the described scenario.

Outdated software (D) may affect performance in some cases, but not directly linked to network congestion in this case.

Inadequate network security (B) isn't likely to cause general slowness related to video traffic.

✅ So, the most likely culprits are E. Incorrect QoS settings and F. Network congestion.