Answer:
Tessellation is possible only for equilateral triangles, squares and regular hexagons. Therefore, there are only three regular polygons that tessellate.
Tessellation is possible, if each interior angle of a polygon is a factor of 360 degrees.
Now, in the given image, pentagon and octagon cannot tessellate.
And the triangle does not seem to be an equilateral triangle. But in general we can say that triangle tessellates.
So, the answer might be triangle (if its equilateral)
