Correct answer is C: A viewpoint defines the perspective from which a view is taken. More specifically, a viewpoint defines: how to construct and use a view (by means of an appropriate schema or template); the information that should appear in the view; the modeling techniques for expressing and analyzing the information; and a rationale for these choices (e.g., by describing the purpose and intended audience of the view).

C is correct

I would say answer D. Togaf book states: An architecture viewpoint is a model (or description) of the information contained in a view. In our example, one architecture viewpoint is the description of how the pilot sees the system, and the other architecture viewpoint is how the controller sees the system

The correct statement about viewpoints is: C. A viewpoint is used as a template to create a view. A viewpoint in architecture represents a perspective or viewpoint from which a specific set of concerns or interests of stakeholders can be addressed. It defines the conventions, rules, and languages for creating architectural views that capture and communicate the relevant information to those stakeholders. A viewpoint provides a framework or template that guides the creation of views, which are visual representations or descriptions of specific aspects of the architecture. These views are then used to communicate and analyze the architecture from the intended perspective.