A Civil 3D _______ is a series of 2D lines, arcs, and spirals typically used to represent a linear feature such as a road centerline.

• A. Profile
• B. Alignment
• C. Corridor
• D. Surface

Answer: (B)

Defining the horizontal path of a linear feature in Civil 3D is done with an alignment—the 2D path made from straight lines, circular curves, and spiral transitions that traces the centerline of a road or similar feature. An alignment captures the plan view geometry, including tangents and curved sections, and can carry stationing information for design and labeling.

Why this fits best: the description explicitly mentions a series of 2D lines, arcs, and spirals used to represent a linear feature in plan view, which is exactly how an alignment is defined in Civil 3D. It serves as the baseline geometry for other design elements, such as profiles (the vertical components along the alignment) and corridors (3D models built from the alignment, a profile, and an assembly).

A profile, by contrast, represents elevation along the alignment rather than the horizontal path itself. A corridor uses the alignment as a path but is a 3D construct that combines the alignment, a profile, and an assembly to model pavement and other features. A surface represents the terrain surface, not the centerline or path geometry.