Revolution method: Rotating an inclined/oblique line or plane about a suitable axis until it becomes parallel to a principal plane reveals its true length or true size. Decide whether this description of “revolution” is correct.

Introduction / Context:
Descriptive geometry offers several techniques—rotation (revolution), auxiliary projection, and folding—to recover true sizes and lengths. The statement claims that revolution determines true length/true size of inclined or oblique elements. We justify why this is correct.

Given Data / Assumptions:

• Target geometry is not parallel to any principal plane.
• We can rotate the geometry about an axis lying in or perpendicular to a plane.
• After rotation, the element becomes parallel to a principal plane.

Concept / Approach:
A line shows its true length only when parallel to the projection plane. A plane shows true shape only when parallel to the projection plane. By “revolving” the element into parallelism, foreshortening disappears and true metrics are read directly on that view.

Step-by-Step Solution:
1) Choose an axis about which rotation will not change known distances.2) Rotate the element until it is parallel to the chosen projection plane.3) Project/trace the rotated position.4) Measure length or area in the rotated (revolved) position; this is the true value.

Verification / Alternative check:
Comparing the result with a two-step auxiliary approach gives identical true metrics, confirming correctness.

Why Other Options Are Wrong:
“Incorrect” / “Only apparent length”: The whole purpose of revolution is to eliminate foreshortening.“Applies to circles only”: The method is general for lines and planes.

Common Pitfalls:
Choosing an inconvenient axis; misreading the rotated trace; forgetting to keep distances to the axis invariant.

Final Answer:
Correct