1. Analysis of the Problem:
- The shadow of the cone is determined by the cone's movement during its revolution and the angle of sunlight.
- As the cone revolves, the shadow extends outward and overlaps during the revolution due to the circular motion and the 45-degree angle of sunlight.
2. Pattern of the Shadow:
- The shadow will cover an elliptical region on the ground, and its shape will be influenced by the 45-degree angle of sunlight, resulting in overlapping areas as the cone completes its revolution.
3. Options Analysis:
- Option A: Shows a simple circular shadow, which is incorrect as it does not account for the 45-degree angle of sunlight.
- Option B: Correctly represents the overlapping elliptical shadow resulting from the cone’s revolution and the sunlight angle.
- Option C: Depicts an elongated shape inconsistent with the motion of the cone.
- Option D: Shows a shape that does not accurately reflect the total shadow region during the cone's revolution.
Conclusion: The correct option representing the total region covered by the shadow is \(B\).