Question

Which solid has one base that is a triangle and three lateral surfaces that are triangles?

Answer 1

If you try to draw the solid being described above, you will see that the sides (given to be triangular) will meet at a common vertex. The solid is therefore a pyramid. Given that the base is a triangle, the pyramid is more specifically referred to as TRIANGULAR PYRAMID. 

Answer 2

I believe it is a triangular pyramid.