What architecture creates separate environments allowing multiple users to work simultaneously without risk to the customer or source code?

The correct answer is tiered architecture, which is designed to separate different levels or layers of functionality within a system. This architecture allows for distinct environments, such as development, testing, and production, enabling multiple users to work on different aspects of a project simultaneously. Each environment operates independently, ensuring that the integrity of the customer data and source code is maintained.

This separation is critical in software development and project management, as it reduces the risk of introducing errors or conflicts that could affect the live product or sensitive information. By isolating the environments, developers can implement changes, test new features, and refine functionalities without jeopardizing the stability of the application or the security of its data.

The other options do not inherently provide the same level of environment separation. Cloud change control and on-premises change control refer to processes rather than architectural structures, while Continuous Integrity/Continuous Delivery focuses on the CI/CD pipeline rather than the separation of environments. Tiered architecture remains the optimal choice for creating safe, simultaneous workspaces for users in a project setting.