Along with the Great Pyramid of Giza. The Sphinx  is one of the most studied ancient monument of mankind's history. The whole complex of Giza, composed of the Sphinx, the Great Pyramid, other pyramids, and distinct structures, definitely holds the key to understanding advanced past civilizations. In the examination of the mystery of the great Sphinx we run into a similar situation. The Egyptians wrote very little about the construction of the Sphinx. However, the Egyptians, Romans, and Arabs did write accounts concerning its numerous restorations, which will be discussed later in this article. In addition, it should be said that other cultures had their form of a Sphinx. For example, the Greek Sphinx was a female with a human head, breast, and the body of a feminine lion. Now there are basically two schools of thought on the origin, the age and the builder of the Sphinx in Egypt. The traditional view of Egyptologists is that Pharaoh Khafre of the Fourth Dynasty built the Sphinx along with the Great Pyramid around 2,500 BC. The evidence is that the face of the Sphinx is thought to look like Pharaoh Khafre. This theory makes the Sphinx about 5,000 years old according to Dr Zahi Hawass, director of Giza Saqqara of the Egyptian Antiquities Organization. The other school of thought doesn't believe that the Egyptians built the Sphinx, but thinks that it was built by an advanced civilization before the Egyptians. The Egyptians came later and built their tombs and temples along the sides of these great structures.   This school of thought has been around for hundreds of years, but new buildings give it more  _ . Recently, Graham Hancock , the author of the famous book Finger-prints of the Gods and some American scholars have presented certain evidence that challenges the traditional thought on the Sphinx. They present proofs that may cause a rethinking of the so-called fact used to determine who built the Sphinx and the Great Pyramid of Giza and for what purpose. Their proofs consist of basically two pieces of evidence astronomical  calculations of the stars and geological evidence that the erosion  of the Sphinx and other monuments of Giza was due to water rather than sand, wind or sunshine according to Robert Bauval's book  _ . It is this evidence that  has turned the Egyptologists' world upside down. Which of the following is the main purpose of the passage?
To show the importance of the Sphinx. To tell us two views on the origin of the Sphinx. To introduce an advanced civilization to us. To explain some mysteries of the Sphinx.