Answer: Rectangular pyramid.
Explanation:
A pyramid is a polyhedron whose lateral faces are triangles and whose base is a polygon (A polygon is a plane shape whose sides are line segments).
When the base of the pyramid is a rectangle, the pyramid is called "Rectangular pyramid".
You can observe in the net of the given solid that its base is a rectangle and it has four lateral faces which are triangles.
Therefore, this solid is:
A Rectangular pyramid.