Explanation
The reason why the alerts are not being received is that the network device is not configured to log that level to the syslog server. The severity level for the events may need to be adjusted in order for them to be sent to the syslog server. References: Network+ Certification Study Guide, Chapter 8: Network Troubleshooting

Explanation
A screened subnet is a network segment that is isolated from both the internal and external networks by firewalls or routers. It is used to host publicly accessible servers that need some protection from external attacks, but also need to be separated from the internal network for security reasons.
References
1: Seven-Second Subnetting - N10-008 CompTIA Network+ : 1.4
2: CompTIA Network+ Study Guide: Exam N10-008, 5th Edition, page 56
3: CompTIA Network+ N10-008 Exam Subnetting Quiz, question 22

Explanation
A VoIP sales call with a customer would be most affected by jitter greater than 10ms on the WAN connection.
Jitter is the variation in delay of packets arriving at the destination. It can cause choppy or distorted audio quality for VoIP applications, especially over WAN links that have limited bandwidth and high latency. The recommended jitter for VoIP is less than 10ms. References: https://www.voip-info.org/voip-jitter/