长城
说到中国文化，不能不提到长城。从公元前7世纪到公元16世纪，在大约2 200年的时间里，先后有19个朝代修建过长城，所修的长城长达10万千米以上。主要的长城修建工程是在秦代、汉代和明代完成的。现今存有遗迹的主要是明长城，从东边入海口的山海关(Shanhai Pass)开始，一直到沙漠深处的嘉峪关(Jiayu Pass)，全长约6700千米。长城是世界历史上最伟大的工程之一，其建造时间之长、参与人数之多、工程难度之大，在世界上无出其右。

When travelling overseas，do you buy water in plastic bottles or take your chances with tap water?Imagine you are wandering about on a Thai island or __26__ the ruins of Angkor.It's hot so you grab a bottle of water from a local vendor.It's the safe thing to do，right?The bottle is __27__ ，and the label says "pure water".But maybe what's inside is not so __28__ .Would you still be drinking it if you knew that more than 90 percent of all bottled water sold around the world __29__ microplastics?

That's the conclusion of a recently __30__ study，which analysed 259 bottles from 11 brands sold in nine countries，__31__ an average of 325 plastic particles per litre of water.These microplastics included a __32__ commonly known as PET and widely used in the manufacture of clothing and food and __33__ containers.The study was conducted at the State University of New York on behalf of Orb Media，a journalism organisation.About a million bottles are bought every minute，not only by thirsty tourists but also by many of the 2.1 billion worldwide who live with unsafe drinking water.

Confronted with this __34__ ，several bottled-water manufacturers including Nestle and Coca-Cola undertook their own studies using the same methodology.These studies showed that their water did contain microplastics，but far less than the Orb study suggested.Regardless，the World Health Organisation has launched a review into the __35__ health risks of drinking water from plastic bottles.

空白处27.应填

as conj.（正当）……的时候；如同；由于
　　________至于，关于
　　________好比是，可谓，在某种程度上