Property of a single contour line: On any one contour line shown on a landform drawing, do all points share the same elevation value?

Introduction / Context:
Contours are fundamental to reading terrain in engineering drawings and topographic maps. Recognizing that a contour is an isoline of constant elevation enables quick interpretation of slopes, ridges, and depressions.

Given Data / Assumptions:

• A contour line is defined as the locus of points of equal elevation.
• Contours are drawn at a fixed contour interval (e.g., 1 m, 5 ft).
• Map drafting adheres to standard cartographic conventions.

Concept / Approach:
Because each contour corresponds to one specific elevation, any movement along that line keeps elevation constant. The spacing between contours communicates slope steepness: close spacing means steep slopes; wide spacing means gentle slopes. Special symbols indicate depressions or closed highs.

Step-by-Step Solution:

Verification / Alternative check:
Check labeled index contours (heavier lines). Every unlabeled intermediate contour between two indices inherits a specific elevation according to the fixed interval; equality holds along each individual line.

Why Other Options Are Wrong:

• Variation along the same contour (option B) contradicts the definition.
• Scale dependency (option C) is irrelevant; the property is definitional.
• Dependence on slope angle (option D) is incorrect.
• Map projection (option E) affects planimetric geometry, not the equality of elevation on one contour.

Common Pitfalls:
Misreading adjacent contours as a single line; overlooking depression hachures that indicate lower elevation inside a closed loop.

Final Answer:
Correct: every point on one contour has the same elevation