It would be "A. A four-sided, tapered monument with a pyramidal tip" that is an example of an obelisk, since this conforms to the definition of the shape itself.
A. A four-sided, tapered monument with a pyramidal tip
Explanation:
An obelisk, is a stony monument shaped like a pillar, square section, with four equal trapezoidal faces, slightly converging, topped top in a small pyramid called pyramidion. They were usually erected on a prismatic stone base. The ancient obelisks were carved from a single block of stone (monoliths). The first that is known is dating to the time of Userkaf, pharaoh of the V dynasty of Egypt (BC 2500 BC). It is unknown how these monuments were erected, as there is no Egyptian documentation describing the method used.
