Which of the following activities is primarily used to invoke and run a separate workflow file?

The activity used primarily to invoke and run a separate workflow file is the option that states "Invoke Workflow File." This activity is specifically designed for scenarios where you want to execute another workflow as part of the current process. By using this activity, you can modularize your RPA solution, making it easier to manage and maintain workflows by separating complex tasks into individual files that can be called as needed.

When you invoke a workflow file, the calling workflow can pass arguments to it, making it flexible and allowing for data sharing between workflows. This approach enhances reusability because once a workflow is created, it can be reused in multiple places without duplicating the code.

Other options, although they might involve running or managing processes, do not specifically pertain to invoking another workflow file. For instance, "Invoke Method" refers more to invoking methods from libraries or APIs rather than a complete workflow file. "Start Workflow" and "Run Workflow" are less specific and don't directly indicate the invocation of a separate workflow file in the same manner that "Invoke Workflow File" does.

Thus, the correct choice highlights the proper usage of managing separate workflow files efficiently, aligning with best practices in RPA.