You are designing a new governance model for your organization's secrets that are stored in Secret Manager. Currently, secrets for Production and Non-Production applications are stored and accessed…

Using separate Google Cloud projects for Production and Non-Production secrets provides the strongest environment separation, facilitates granular IAM access control at the project level, and allows for independent management of Cloud KMS keys (CMEK) and their rotation schedules for each environment, fulfilling all requirements.

Using a single Google Cloud project for both Production and Non-Production secrets makes it significantly harder to maintain strict environment separation and granular access control, requiring more complex and error-prone IAM policies to prevent cross-environment access.

(Assuming C is similar to A in starting with separate projects but differing in the truncated second part, without full text, it's hard to distinguish from A. If it's identical, it's a duplicate. Assuming A is the definitive best answer for the first part.) This option starts correctly by separating projects, but without the full second part, its overall effectiveness cannot be fully assessed; however, option A is deemed the best holistic solution.

Similar to B, using a single Google Cloud project combines environments, making it challenging to achieve the required strict separation, granular access, and independent key rotation schedules efficiently.