A. Apply the patches to the production systems apply them in a staging environment, and then test all of them in a testing environment

B. Apply the patches to systems in a testing environment then to systems in a staging environment, and finally to production systems.

C. Test the patches m a test environment apply them to the production systems and then apply them to a staging environment

D. Test the patches in a staging environment, develop against them in the development environment, and then apply them to the production systems