题目

阅读短文及文后选项，选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。The Silk Road is the name of different roads that long ago connected Europe, Africa and Asia.【1】. Scientists believe people began to travel the Silk Road about 3,000 years ago. By the time the Chinese silk trade became important in the world, the Silk Road covered almost 6,500 kilometres. It spread from Rome to China, which is from the West to the Far East.【2】 They also carried and traded spices (香料), cloth, valuable stones and gold. There is a famous old story along the o直径所对的圆周角等于    度．