Comprehensive and Detailed Explanation From Exact Extract:

SRE-led service automation focuses on making environments reproducible, reliable, and consistent. One of the key principles aligned with Google SRE practices is the use of Infrastructure as Code (IaC), which allows environments to be provisioned automatically, consistently, and predictably.

The Site Reliability Engineering Book, in its discussions on automation, states:

“Automation implemented as code ensures that environments are consistent, repeatable, and less prone to human error.”

The SRE Workbook expands on this concept:

“Infrastructure as Code allows services to scale and evolve reliably by ensuring that configuration and infrastructure changes are automated and version-controlled.”

IaC is fundamental to:

Reducing toil

Increasing reliability

Enabling consistent automation across environments

Reducing configuration drift

Why the other options are incorrect:

A SRE supports testing in production; it does not ban automated tests.

C Using unsigned artifacts violates security and reliability best practices.

D Adding hardware is not an automation principle and contradicts efficiency goals.

Thus, the correct answer is B.