Read the passage, then choose the correct options. Write your answer in the box. 

         One of the 7 wonders of the ancient world, the great pyramid of Giza was a monument of wisdom and prophecy built as a tomb for Pharaoh Cheop in 1720 BC. Despite its antiquity, certain aspects of this construction makes it truly one of the truly great wonders of the world. The thirteen – acre structure near the Nile river is a solid mass of stone blocks covered with limestone. Inside are a number of hidden passageways and the burial chamber for the pharaoh. It is the largest single structure in the world. The 4 sides of the pyramid are aligned almost exactly on true north, south, east and west – an incredible engineering feat. The ancient Egyptians were sun worshipers and great astronomers, so computations for the great pyramid were based on astronomical observations.            Explorations and detailed examinations of the base of the structure reveal many intersecting lines. Further scientific study indicates that these represent type of timeline of events – past, present and future. Many of the events have been interpreted and found to coincide with known facts of the past. Others are prophesied for future generations and currently under investigation. Many believe that pyramids have supernatural powers, and this one is no exception. Some researchers even associate with its extraterrestrial being of the ancient past.              Was it superstructure made by ordinary beings, or one built by a race far superior to any known today. 

What has research of the base reveal?