It took years 【小题1】(complete) the Qinghai-Tibet Railway. The construction workers 【小题2】(overcome) the most difficult engineering challenges，one of which was how to protect the delicate ecosystem.To allow the wild animals to move safely and freely in their 【小题3】(nature) habitat，they built thirty-three passages under the railway. To prevent damage to wetlands and grasslands，675 bridges with a total length of about 160 kilometres 【小题4】(build) between Golmud and Lhasa. They even moved 140，000 square metres of wetland to 【小题5】 new area in order to protect its distinct ecosystem. 【小题6】(locate) at over 5，000 metres above sea level，Tanggula Station is the highest railway station in the world. In locations such as this，the thin air，changeable weather and high levels of UV radiation presented perhaps the 【小题7】 (great) challenge for railway workers. To make sure they stayed healthy，several oxygen-making stations were constructed. To protect Cuona Lake 【小题8】 construction waste，the railway workers used thousands 【小题9】 thousands of sandbags to build a twenty-kilometre wall along the lake. In a word，the railway workers built our “impossible” railway with the care that the environment deserves. It 【小题10】(true) is an extraordinary “Sky Railway”.

A desert doesn’t sound like the most promising place to plant a tree. Yet, since 1978, China 【小题1】(plant)at least 66 billion of them across its desert northern territories, hoping to transform its sandy dry land and yellow dunes 【小题2】 a Great Green Wall.

Ian Teh 【小题3】(record)this amazing undertaking while traveling through northern China last year. His expansive photographs show workers tending young trees, blasting them with water and 【小题4】(fill)irrigation tanks. “【小题5】 planting trees sounds great on paper, you can feel doubtful,” Teh says. “When seeing in person, it was impressive.”

The tree-planting strategy is a massive attempt to help fight desertification. 【小题6】 (rough) a million square miles of China—a quarter of the country—【小题7】(cover)in sand. Drought, deforestation, overgrazing and other 【小题8】(problem)threaten an additional 115,000 square miles, fueling very cruel and 【小题9】(violence)sandstorms that regularly blast cities like Beijing and Dunhuang. Many scientists are feeling doubt that planting trees will make a difference in 【小题10】 long run. But China’s State Forestry Administration claims the measure has reduced sandstorms by 20 percent and desertification by nearly 5,000 miles in recent years.

Many people like travelling abroad. The extra money 【小题1】 (bring) in can be of great benefit to these countries. However, tourism has not been good news for the environment. First, transporting millions of tourists to their holiday destinations 【小题2】 (pollute) the air and the seas. Secondly, some beautiful landscapes are destroyed forever due to the newly-built hotels. And finally, fresh water supplies are running low 【小题3】 tourists consume much water. To conclude, I think tourism has a lot of negative consequences on nature. If we want our planet to be a 【小题4】 (health) place, we need to travel less.