The world-known Silk Road across the Eurasian Continent is a friendship bridge____ (link) the Europe and Asian people. It is one of the most important theme tourist routes in the world and the most____(value) tourist product in China. From the time Zhang Qian____(open) up the world-famous Silk Road during the Han Dynasty, until the collapse of the Yuan Dynasty, it enjoyed ____ history of about 1,600 years.

    Silk Road with____(it) 2,000 years history has witnessed the historical changes and the progress of cultures ____(exchange) between China and the Western countries. The section in China, many ethnic cultures____ (include), is also as a jade belt. The peoples of these ethnic groups such as Mongolians, Huis, Uygurs, Hazaks have maintained their unique traditions and cultures, living habits and religious beliefs____ are from the soul of the Silk Road and attract many tourists to visit. In fact____the Silk Road in the northwest of China, there are another two trade roads in the southwest of China and by sea, which also contribute____ (great) to the development of the world. They are called the “Southern Silk Road” and the “Silk Road on the Sea”.

1795年，印度人均消费英国棉纱、棉布的量巨大，而中国消费英国棉纱、棉布的量基本为零。中国消费英国棉纱、棉布的量基本为零的背景是(    )

t℃时，在饱和硫酸铜溶液中加入a g无水硫酸铜，恢复至原温度可析出b g硫酸铜晶体。说法正确的是（   ）