Which phase of the waterfall approach specifies the required order of events between program components?

The correct choice is related to the design phase of the waterfall approach. In this phase, the architecture and design of the system are addressed, which includes establishing the necessary order of events and interactions between various program components. It involves creating detailed specifications and working on a blueprint for the system, which is crucial for successful implementation later on.

The design phase delves into how the components will work together, including defining data flow, control flow, and any dependencies that exist. This structured planning is essential to ensure that once the implementation begins, developers understand the sequence of operations necessary for the system to function correctly.

In contrast, while the implementation phase focuses on coding the system based on the earlier designs, it does not primarily address the sequencing of events. Similarly, the testing phase occurs after implementation, where the system is evaluated for functionality and bugs without modifying the order of events defined in design. The requirements gathering phase mainly concentrates on defining what the system should do rather than how the components interact and execute their functions.

Thus, establishing the required order of events between program components is a critical aspect of the design phase, making it the correct choice in this context.