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

A pyramid is a polyhedron whose base is a polygon and its lateral faces are triangles. we have 4 congruent equilateral triangle, as per definition of pyramid if we add a square with same side length of a triangle we get a polygon as its base and it will make pyramid.

Option (a) is not enough to make pyramid as per solution.

(b) is the correct answer and it is enough to make pyramid.

(c) is not enough to make pyramid as per solution.

(d) is not enough to make pyramid as per solution.