It took years     1    (complete) the Qinghai-Tibet Railway. The construction workers     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     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     4    (build) between Golmud and Lhasa. They even moved 140，000 square metres of wetland to     5     new area in order to protect its distinct ecosystem.     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     7     (great) challenge for railway workers. To make sure they stayed healthy，several oxygen-making stations were constructed. To protect Cuona Lake     8     construction waste，the railway workers used thousands     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     10    (true) is an extraordinary “Sky Railway”.

【推荐3】阅读下面材料，在空白处填入适当的内容（不多于3个单词）或括号内单词的正确形式。

Ms. Mary was over eighty, but she still drove her old car like half her age. She loved driving very fast, and boasted of the fact     1    she had never, in her thirty-five years of driving, been punished     2    a driving mistake.

Then one day, she nearly lost her record. A police car followed her, and the policemen in it saw her pass a red light without     3     (stop).

When Ms. Mary came before the judge, he looked at her     4    (severe) and said that she was too old to drive a car, and that the reason     5    she had not stopped at red light was most probably that her eyes had become weak with old age,     6    she had simply not seen it.

When the judge had finished what he was saying, Ms. Mary opened the big handbag she was carrying and took out her sewing. Without saying a word, she     7     (choose) a needle with a very small eye, and threaded it at the first time.

When she had successfully done this, she took the thread out of the needle again and handed     8    the needle and thread to the judge, saying, “Now it is your turn. I suppose you can drive     9    car well, and you have no doubts about your eyesight.”

The judge took the needle and tried to thread it. After half a dozen times, he had still not     10    (success). The case against Ms. Mary was dismissed, and her record remained unbroken.