A platform team must deploy a standard monitoring stack to every account in selected Organizations OUs, including newly added accounts. Which capability best fits?

1. Use one EC2 Auto Scaling group to create every cross-account resource.
2. Copy the template into a shared bucket but never create stack instances.
3. Use service-managed StackSets with appropriate OU targets and automatic deployment configuration.
4. Create a stack export in one account and assume it creates resources in every OU.