There are many possible answers.
NO!!! A triangle is a 2-dimensional shape of three sides; archaically a 'trigon'. A polyhedron is a 3-dimensional solid of many sides.
The answer is a polyhedron
it is a triangle prism
square and hexagon
Tetrahedron
Yes
It is a face of the polyhedron
Each surface of a polyhedron is called a face.
pyramid
Tetrahedron
A 3D triangle, commonly referred to as a tetrahedron, has four flat surfaces. Each surface is a triangle, and the tetrahedron is the simplest form of a polyhedron. It consists of four vertices and six edges as well.
Its surface, would you believe!