A photo-sharing site delivers content worldwide from a library on Amazon S3 using Amazon CloudFront. Users are trying to access photos that either do not exist or they are not authorized to view.
What should be monitored to better understand the extent of this issue?

A. GetRequestsS3 metric on Amazon CloudWatch
B. 4XXErrorRateCloudFront metric on CloudWatch
C. 5XXErrorRateCloudFront metric on CloudWatch
D. PostRequestsS3 metric on CloudWatch