Apple Business Manager (ABM) is Apple's web-based portal designed for IT administrators in businesses to manage device enrollment (via Automated Device Enrollment), purchase and distribute app licenses, and assign content like books. Apple School Manager (option C) serves a similar purpose but is tailored for educational institutions. Apple Configurator (option B) is a macOS app for device configuration, not a portal. There's no "Managed Apple ID portal" (option D); Managed Apple IDs are managed within ABM or ASM. The question's broad scope fits ABM for business contexts, as per the Apple Platform Deployment Guide.