Analogy: Arc is to Circle as Line is to ____. Select the figure of which a line is a constituent boundary/part, analogous to an arc being a part of a circle.

Introduction / Context:
This analogy focuses on “part–whole (boundary) relationships” in geometry. An arc is a continuous part of a circle’s circumference. We need a figure for which a straight line (or line segment) serves an analogous boundary role.

Given Data / Assumptions:

• An arc is a portion of a circle’s boundary (curved).
• A line (interpreted as a straight boundary/edge) can bound polygons.
• We seek a shape whose boundary is made from straight lines.

Concept / Approach:
Circles have curved boundaries; arcs are their parts. Polygons have straight-line edges; rectangles are quadrilaterals with four straight sides and four right angles. Thus, a line segment relates to a rectangle’s boundary the way an arc relates to a circle’s boundary.

Step-by-Step Solution:
Identify role: “arc : circle” = “edge component : entire figure.”Polygons (e.g., rectangles) consist of line segments as boundary parts.Hence “line : rectangle” mirrors “arc : circle.”

Verification / Alternative check:
Check alternatives: ellipse has curved boundary (no straight line segment part); sphere is 3D (surface not composed of lines); a point is dimensionless, not a figure composed of lines.

Why Other Options Are Wrong:
Point: not a composite figure. Ellipse: boundary is entirely curved—no line segments. Sphere: 3D surface; the analogy is 2D boundary-based.

Common Pitfalls:
Confusing “line” with “tangent to circle” (external relation) rather than “edge of a polygon” (internal boundary part). The analogy is strictly part–whole.

Final Answer:
Rectangle.