The figure below shows a solid. Which one of the following is a net of the solid?

1. Identify the solid and its faces

The solid is a triangular pyramid (tetrahedron). It has 4 faces, all of which are triangles.

2. Evaluate the given options based on the faces

Option (2) contains a square and rectangles, which do not match the solid's triangular faces. Option (3) only has 3 triangles, but the solid has 4 faces.

3. Determine the correct net by mental folding

Option (1) folds into a tetrahedron but the arrangement shown (diamond shape) is a valid net for a tetrahedron. However, Option (4) is the classic net of a tetrahedron: a central base triangle with three triangular faces attached to its sides, which fold up to meet at a single top vertex. Both (1) and (4) can form a tetrahedron, but (4) is the standard representation of the net of a regular triangular pyramid as shown in the figure.