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”.

It's common to see food delivery workers riding electric bikes in a hurry through big cities in China. Some of them even risk     1     (run) red lights to deliver their meals in time. However, such careless behavior often causes serious problems.

The reason for the rise of such a careless behavior is that there is     2     large demand for food delivery workers, and many companies offer high salaries     3    (attract) new workers.

In fact, food delivery workers are often under high     4    (press) from their employers. They face company fines for delivering food late. Moreover, the more orders they take, the more money they can earn,     5     leads to some workers checking     6    (they) mobile phones for new orders while they are riding their bikes

While most companies require delivery workers to follow traffic rules, it remains a problem whether these requirements and rules are     7    (strict) obeyed

To solve the problem, some cities     8    (take) action since last year. Shanghai required the delivery workers should    9    (train) on traffic rules and safety. Now in Shenzhen, if a delivery worker gets caught breaking traffic rules more than twice, he or she will be banned     10     driving food delivery vehicles for a whole year.