A screened subnet is a network segment that separates two different environments, such as OT (operational technology) and IT (information technology), and provides security controls to limit and monitor the traffic between them. This would allow the business to get the required reports from the historian server without exposing the OPOT environment to unnecessary risks. Using a VPN, allowing IT traffic, or allowing PLCs to send data are less secure options that could compromise the OT environment. Verified Reference: https://www.comptia.org/blog/what-is-operational-technology https://partners.comptia.org/docs/default-source/resources/casp-content-guide