Final answer:
A requirements document that confines the scope to what the system can deliver is said to be 'achievable', ensuring it is realistic, supports other system goals, and has a definite timeline.
Step-by-step explanation:
If a requirements document confines the scope of what your system can deliver, it is said to be achievable. Such a document ensures that the system requirements are realistic and attainable and that any barriers can be overcome with the available resources and technology. To be achievable, the requirements must also be relevant, supporting other goals of the system and making sense within its context. Furthermore, they must be time-bound, which means they have a specific target date or deadline by which the system is expected to fulfill these requirements.