A research company conducts mathematical simulations in the AWS Cloud.

Launch new EC2 instances. Generate an individual SSH key for each new EC2 instance. Store the SSH key in AWS Secrets Manager. Create a new IAM policy. Attach the IAM policy to the engineers' IAM role with an Allow statement for the GetSecretValue action. Instruct the engineers to retrieve the SSH key from Secrets Manager when the engineers connect through any SSH client.

Create an AWS Systems Manager document to run commands on EC2 instances to set a new unique SSH key. Create a new IAM policy. Attach the IAM policy to the engineers' IAM role with an Allow statement to run Systems Manager documents. Instruct the engineers to run the document to set an SSH key and to connect through any SSH client.

Launch new EC2 instances without setting up any SSH key for the new EC2 instances. Set up EC2 Instance Connect on each new EC2 instance. Create a new IAM policy. Attach the IAM policy to the engineers' IAM role with an Allow statement for the SendSSHPublicKey action. Instruct the engineers to connect to the EC2 instances by using Instance Connect from the AWS CLI.

Set up AWS Secrets Manager to store the EC2 SSH key. Create an AWS Lambda function to create a new SSH key and to call AWS Systems Manager Session Manager to set the SSH key on the EC2 instance. Configure Secrets Manager to use the Lambda function to automatically rotate the SSH key once daily. Instruct the engineers to retrieve the SSH key from Secrets Manager when the engineers connect through any SSH client.

CC is correct because EC2 Instance Connect is designed to provide per-connection, short-lived SSH access without long-lived shared private keys, and it integrates with IAM so access is controlled and auditable. With EC2 Instance Connect, engineers push a public key for a short time window to the target instance using the SendSSHPublicKey API action. This meets the “unique SSH key per session” intent because the key can be generated per session and injected temporarily instead of being a persistent static key. Additionally, the key injection is performed through an AWS API call, which is recorded in AWS CloudTrail, satisfying the logging requirement for SSH access activity.Why the other options are incorrect:

B: Running a Systems Manager document to set keys creates operational overhead and still does not inherently ensure CloudTrail logs of each SSH connection (the SSM Run Command API calls are logged, but the subsequent SSH login over the network is not an AWS API event). It also risks key persistence beyond a single session.

D: Daily rotation is not “unique per session,” and it is complex/operationally heavy. Like A, the SSH login itself is not automatically a CloudTrail event; CloudTrail would capture Secrets Manager and SSM API calls, not the network SSH authentication event.