Descriptive Geometry — Any planar inclined surface can be shown in true shape by choosing an auxiliary view whose projection plane is parallel to that surface.

Introduction / Context:Inclined planar faces appear foreshortened in principal views. Auxiliary views remove this foreshortening by aligning the projection plane parallel to the face, revealing true shape for accurate dimensioning.

Given Data / Assumptions:

• The surface of interest is planar (not warped).
• Projection remains orthographic with parallel projectors.
• The auxiliary plane is chosen parallel to the target surface.

Concept / Approach:True-length edges lie in planes parallel to the projection plane. By orienting the auxiliary plane accordingly, both edges and areas show actual size and shape.

Step-by-Step Solution:1) Identify the inclined plane.2) Define an auxiliary plane parallel to it.3) Project all key points using parallel lines.4) Connect points to produce the true-shape outline and dimension.

Verification / Alternative check:Compare measured lengths on the auxiliary with model distances; they should match exactly if the plane is parallel.

Why Other Options Are Wrong:It is not limited to horizontal or circular features and does not involve perspective methods.

Common Pitfalls:Accidentally selecting a skewed plane; mixing auxiliary and principal dimensions; omitting necessary datums.

Final Answer:Correct