Which az acr purge option removes manifests that are untagged and older than 7 days from the 'myapp' repository?

1. ✓ A az acr purge --filter 'myapp:.*' --ago 7d --untagged (correct answer)
2. B az acr image delete --age 7d
3. C az acr retention apply --days 7
4. D az acr purge --ago 7d

Shortcut: az acr purge with --filter, --ago, and --untagged removes untagged manifests older than the specified period from matching repositories.