单选题：根据以下材料回答第 1～4 题：Passage Four Would you like to spend all eve

根据以下材料回答第 1～4 题：
Passage Four
Would you like to spend all evening reading a lovely story with beautiful illustrations and make $35，000 at the same time? Millions of people all over the world tried to do just that．Only orle succeeded．The book is called Masquerade，and was written by British painter Kit Williams．Within its pages are clues to the location of a golden jewel，and who—ever figured out the clues could find and keep the treasure．
Some years ago，Williams was asked to write a children’s book．Wanting to do some thing no one else had done before，he decided to bury a golden treasure and tell where it was in the book．He began painting without a clear idea of war the story would be about， where he would bury the treasure，or even whet the treasure would be．As he painted，he decided that in the story a hare，or rabbit，would travel through earth，air，fire and water to deliver a gift from the moon to the sun．
After three years，he finished the paintings and then wrote the story．The treasure became an l 8carat gold hare，adorned with precious stones，and it was made by Kit Wil— ltams himself．This beautiful jewel，worth around $35，000，depending on gold prices，was buried somewhere in Britain，free to anyone who could decipher the clues．Williams’s book kept people of all ages amused trying to solve the mystery of Masquerade．
The rabbit was finally found in the spring of 1982，by a 48～year-old design engineer．It was buried in a park about thirty-five miles from London．
The function of the first sentence in this passage is to ．