Part Four文化背景题。（每题6分）
请对下列文化背景方面的名词进行简要解释。
1. Christmas
2. 10 Downing Street

答案 1. Most people know that the simple meaning of Christmas is to celebrate the birth of Jesus Christ, the son of God in the Christian religion. The word Christmas originated from an old English phrase, "Cristes Masse", meaning the mass of Christ（基督弥撒）. The date, December 25, was established by Bishop Liberius of Rome in 354 AD. He selected the date to mark the official time for celebrating Christ's birth. Before then, the birth of Jesus was observed on different days and even to this day no one is certain the exact date of Christ's birth. The name of the holiday is often shortened to Xmas because Roman letter "X" resembles the Greek letter X, an abbreviation for Christ. 2. 10 Downing Street has been the heart of government for over a century as the meeting place of the Cabinet and as a reception venue for VIPs from around the world. It is the workplace for the many staff that supports the Prime Minister and it is also the home of the Prime Minister and his family. Margaret Thatcher called the place “one of the most precious jewels in the national heritage”. Its black front door with a number 10 on it has become a symbol of the British Prime Minister and the government.In a survey of the top ten film spot in October, 2007, 10 Downing Street was named in fourth in the poll thanks to its appearance in Love Actually.