You need to reduce ACR storage costs. Untagged manifests accumulate from repeated CI builds. Which approach removes them on a schedule with the least custom code?

1. A A Logic App calling the ACR REST API nightly
2. ✓ B An ACR Task running 'az acr purge --untagged --ago 7d' on a cron schedule (correct answer)
3. C Manually running docker image prune
4. D Downgrading the SKU to Basic

Shortcut: az acr purge is packaged as a container that ACR Tasks can run on a timer trigger. It handles untagged manifests and age filters natively, with no external orchestration.