Final answer:
The correct AWS service for monitoring an Amazon EC2 instance's CPU and network utilization is Amazon CloudWatch, which offers metrics, logs, alarms, and automated responses to changes in AWS resources.
Step-by-step explanation:
To monitor a new Amazon EC2 instance's CPU and network utilization, the correct AWS service to use is Amazon CloudWatch. Amazon CloudWatch provides monitoring for AWS cloud resources and the applications running on AWS. It enables you to collect and track metrics, collect and monitor log files, set alarms, and automatically react to changes in your AWS resources. CloudWatch can monitor EC2 instances and provide data regarding the instance's CPU, disk, network, and other resources usage. You can use this data to see how the instance's performance changes over time and to set alarms that let you know when the usage reaches defined thresholds.