Which of the following services can be used for monitoring VPN connections

Answer options:

A.VPC Flow Logs
B.AWS WAF
C.AWS Config
D.AWS Cloudwatch

Answer - D
The AWS Documentation mentions the following
You can monitor VPN tunnels using CloudWatch, which collects and processes raw data from the VPN service into readable, near real-time metrics. These statistics are recorded for a period of 15 months, so that you can access historical information and gain a better perspective on how your web application or service is performing. VPN metric data is automatically sent to CloudWatch as it becomes available.
For more information on monitoring VPN Connections, please refer to below URL:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/monitoring-cloudwatch-vpn.html