The points −1,0,1,0,1,−1,1,−1,0,23,23,23form a

Given points are  A−1,0,1,B0,1,−1,C1,−1,0,D23,23,23The lengths of the sides        AB=1+1+4=6BC=1+4+1=6AC=4+1+1=6       The vertices A, B, C forms an equilateral triangle, and the fourth vertex D does not lies in the plane determined by A, B, CHence, the figure formed by these four vertices is tetrahedron.