Final answer:
A external dependency is not linked to tasks within the same project file but to tasks in another project file, representing a relationship where one project's task is dependent on another project's task.
Step-by-step explanation:
The correct answer to the student's question is c) External Dependency. An external dependency is a relationship in project management where a task in one project relies on the start or finish of a task in another, separate project. Unlike an internal dependency, which links tasks within the same project, an external dependency links tasks across different project files.
In practice, this means that if the external task that your project is dependent on is delayed or changed, it can affect the scheduling and progression of your project. It is crucial to identify and manage external dependencies to ensure that the project stays on track.
Software like Microsoft Project allows project managers to link tasks between different project files, establishing these external dependencies directly within the project management tool to keep track of them efficiently.