Step-by-step explanation:
Any polygon that has exactly 3 sides is called a triangle. Here you haven't provided any figure, so I'll assume that we have two triangles as indicated in the figure below. As you can see, we have two sides:
When placing together we realize that those sides measures the same, so:
So
is the diagonal of the shape. From the figure we also know that opposite sides are equal and parallel, therefore, this shape represents a parallelogram. Remember that a parallelogram is a quadrilateral where both pairs of opposite sides are parallel.
So correct option is:
Parallelogram