Which AWS service should the company use to meet these requirements?

Explanations:

AWS Artifact provides on-demand access to AWS’s compliance reports, but it does not monitor network or account activity for security threats.

Amazon Macie is used for discovering and protecting sensitive data like personally identifiable information (PII), but it does not monitor network or account activity.

AWS Identity and Access Management (IAM) is used to manage access to AWS services and resources but does not actively monitor for security threats.

Amazon GuardDuty is a continuous security monitoring service that analyzes network and account activity to detect potential security threats, making it the correct choice.