The correct option is B Triangle
As ribbons are to be used on the borders of both the shapes (the triangle and the square), which means that the length of the ribbon used on either shape will be equal to the perimeter of that shape.
Hence, we just have to compare the perimeters of both the shapes to know which one of them used more ribbon.
Given, side of the triangle = 3 cm
In an equilateral triangle, the length of all the sides are equal.
So, perimeter = side + side + side
⇒ Perimeter = 3cm + 3 cm + 3 cm = 9 cm
Each side of the square = 2 cm
Perimeter = side + side + side + side
⇒ Perimeter = 4 × side = 4 × 2 = 8 cm
As, perimeter of the triangle > perimeter of the square,
the triangle will require more ribbons.