Comprehensive and Detailed Explanation From Exact Extract:

Using verified and signed artifacts is essential for safe automation, ensuring that deployments are consistent and free of dependency or supply chain errors. This is a fundamental principle in Google’s release engineering and SRE practices.

The Site Reliability Engineering Book, chapter “Release Engineering,” states:

“Releases should be built once, tested, signed, and stored in a secure repository. Only signed and verified artifacts should be promoted to production to prevent configuration drift and dependency inconsistencies.”

The SRE Workbook echoes this:

“Automated promotions depend on the integrity and immutability of artifacts. Signed artifacts ensure consistency and prevent errors related to mismatched dependencies.”

Why the other options are incorrect:

A External visibility is irrelevant and may create security risks.

C Error budgets relate to reliability, not artifact promotion.

D SLOs do not define artifact signing; this is handled by release engineering processes.

Thus, the correct answer is B.