Answer:
Every triangle tessellates.
Explanation:
There are only three regular polygons that tessellate - equilateral triangles, squares and regular hexagons. Tessellation is an arrangement of closely fitted polygons without overlapping.
Only equilateral triangles tessellate out of the given options. For a tessellation to be possible, the interior angle of the polygon must divide 360 degrees evenly.
The internal angle of equilateral triangle is 60 degrees and it completely divides 360 degrees.

So, triangles is the answer.