**Question:**

We have 4 congruent equilateral triangles. What do we need more to make a pyramid?

(a) An equilateral triangle.

(b) A square with same side length as of triangle.

(c) 2 equilateral triangles with side length same as triangle.

(d) 2 squares with side length same as triangle.

**Solution:**

(b) We know that, a pyramid is a polyhedron, whose base is a polygon and lateral faces are triangles. But in the question, we have only 4 congruent

equilateral triangles. Thus, we have to add a polygon in the base of atleast a four-sided figure.

Hence, option (b) is required to make a pyramid.