The correct option is Convex mirror.
Explanation
The suitability of a mirror for viewing a large object depends on its field of view and the nature of the image formed (magnification and orientation). Spherical mirrors alter the size and field of view based on their curvature.
Detailed Analysis:
- Convex Mirror: A convex mirror curves outward and always forms a virtual, erect, and diminished (smaller than the object) image. Crucially, it offers a wider field of view than plane or concave mirrors. This property allows a small surface area to capture the complete image of a large, tall object, such as a distant building.
- Plane Mirror: To view the full-length image of an object in a plane mirror, the mirror must be at least half the height of the object. Consequently, a small plane mirror is insufficient to view a tall building in its entirety.
- Concave Mirror: For a distant object, a concave mirror forms a real, inverted, and diminished image at its focus. While the image is reduced in size, the inverted orientation and narrower field of view compared to a convex mirror make it less suitable for this specific purpose.
Key Takeaway:
Convex mirrors are uniquely suited for viewing full-length images of tall, distant objects because they provide a wide field of view and produce erect, diminished images.