Final answer:
The 'Irregular tombstones of tenfold pageantry' best match with Egyptian pyramids, which were designed as monumental tombs for pharaohs, rich in historical pageantry and variety.
Step-by-step explanation:
The phrase 'Irregular tombstones of tenfold pageantry' seems to suggest a connection to mortuary practices or structures associated with death and commemoration. Considering the cultural references provided, the best match is A) Egyptian pyramids. These monumental structures have been the graves of pharaohs and are rich in historical pageantry. The pyramids, particularly the Great Pyramids at Giza, were constructed during the Old Kingdom and were designed as tombs for pharaohs, showcasing their wealth and preparing them for the afterlife. The closest association to 'irregular tombstones' would be the various shapes and sizes of the pyramids, as well as other mortuary complexes in Egypt, like the mortuary temple of Hatshepsut and the elaborate tombs found in the Valley of the Kings.