You don't want programmers to have access to production resources. What's the easiest way to do this in Google Cloud?

Set up private access and Identity-Aware Proxy.

Use different service accounts for production and development resources with your project.

Create development and production projects, and don’t give developers access to production. ✓

Create a firewall rule that blocks developer access to production servers and databases.

Correct
This is the correct answer, because the simplest way is to have separate projects and not give developers access to the production project.