Correct answer - "Use a cron job on the instances that push the EC2 RAM metric as a Custom
metric" : The Amazon CloudWatch Monitoring Scripts for Amazon Elastic Compute Cloud (Amazon EC2)
Linux-based instances demonstrate how to produce and consume Amazon CloudWatch custom metrics.
These Perl scripts comprise a fully functional example that reports memory, swap, and disk space
utilization metrics for a Linux instance. You can set a cron schedule for metrics reported to
CloudWatch and report memory utilization to CloudWatch every x minutes.
"Use instance metadata ram disk-id" - This can be retrieved by the instance metadata but it is
just an ID of the RAM disk specified at launch time
"Access as a standard CloudWatch metric" - AWS CloudWatch provides most of the monitoring Metrics
by default but it doesn't have any metrics for memory utilization details
"Use X-Ray" - This service helps with Identifying errors and bugs