The correct answer is: A. the metrics obtained by cloudwatch may be used to enable a feature called auto scaling
CloudWatch is a monitoring service that provides data and actionable insights about your AWS resources, applications, and infrastructure. You can use CloudWatch to collect and store metrics, events, and logs from your AWS resources and applications. You can also use CloudWatch to set alarms, visualize your data, and create automated actions based on your data.
Auto Scaling is a service that automatically adjusts the number of Amazon EC2 instances that are running in your Amazon Elastic Compute Cloud (EC2) environment based on demand. You can use Auto Scaling to maintain a consistent level of performance for your applications, even as the demand for your applications changes.
You can use CloudWatch metrics to trigger Auto Scaling events. For example, you can create an Auto Scaling policy that launches an additional EC2 instance when the average CPU utilization of your EC2 instances exceeds 80%.
However, you cannot use CloudWatch metrics to enable Auto Scaling. Auto Scaling is a separate service that you must enable and configure separately from CloudWatch.
The other options are all correct.
B. A number of tools are used to support EC2 services. These tools include the Amazon EC2 Management Console, the Amazon EC2 Command Line Interface (CLI), and the Amazon EC2 API.
C. Amazon machine instances are sized at various levels and rented on a computing/hour basis. You can choose from a variety of instance types, each with its own set of CPU, memory, and storage capacities. You can also choose to rent your instances on a monthly or hourly basis.
D. None of the mentioned.