China was the first country in the world to produce silk. Several centuries, Chinese ________ was the most popular product which was taken to the West.

Zhang Qian, a famous traveler, first “________” the Silk Road. From then on, the Silk Road ran ________ different countries. The Silk Road was ________ as China’s “national road”. It was the most ________ connection between the East and the west.

Many businessmen traveled in large caravans（车队） in the past. They ________ a lot of products along the Silk Road. The caravans took silk to the ________. From the West, the caravans brought back gold, colored glass and European food.

Central Asia was in the middle part of the Silk Road. The caravans ________ silk and other products and traveled from China through Central Asia to the West. There were ________ main routes—the northern route, the central route and the southern route. The Silk Road was not only very ________ for businessmen to trade their products, but also very important routes which spread different cultures.

You might like to listen to music while studying. What kind of music is your favorite? An experiment（实验）found that listening to classical music at work can _________ efficiency（效率）by 15%.

A survey of 2, 000 British workers found that half of them listen to music _________ they are at work. Some of their bosses（老板）_________ them to do so, while others are against it. They believe it has a bad influence（影响）on their _________. British doctor Becky Spelman did an experiment to find out _________ background（背景）music hurts or improves efficiency.

In the experiment, four office workers needed to copy two 600-word sets of _________. The group worked on the first passage with no music playing and worked on the _________ one with classical music playing in the background. It _________ them an average（平均的）time of 20 minutes and 59 seconds to finish the first set. But the average time for the second was 17 minutes and 42 seconds.

Classical music can work as a kind of white noise, ___________ Spelman. White noise is a mixture of sounds with different frequencies（频率）. It can help people stay focused（集中精力的）.

__________, as long as the music has a calm（镇静的）beat, it can help us keep calm. “This makes it easier for us to focus on what we’re doing,” Spelman said.

The weather is _______ in different parts of the world. In some places it is _______, and in others it is humid (潮湿的). If the weather is too dry, the land will not be _______ for animals or plants. In humid weather, there may be too much _______. The rivers go over their sides. The _______ may take the bridge away. If the rivers go over their sides, a lot of people may not have enough food. If there is very dry weather for a long _______, the river beds may be dry. In some _______ parts of the world, the weather may be very cold. There may be _______. When it snows, the trees, the buildings and everything look _______. In winter the days are ________ and the nights are long. ________ cold weather nights, when there are no clouds or winds, the ________ is very clear (晴朗的). And the moon and the stars ________ very beautiful. People may ________ their coats and go out for a long walks. When they come back to their houses, they may be happy to have ________ coffee and cakes by the fire.