题干

在提取叶绿素的实验中,下列操作方法及其目的错误的是(   )

A:研磨时加入二氧化硅,目的是使研磨充分

B:研磨时加入碳酸钙,目的是保护色素免遭破坏

C:制备滤纸条时要将滤纸条的一端剪去两角,目的是使色素在滤纸条上扩散均匀

D:分离色素时可让滤纸条上的滤液细线接触到层析液,目的是使色素带更加清晰

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D

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      The concept of solitude(独处) in the digital world is almost non­existent. In the world of digital technology, e­mail,social networking and online video games, information is meant to be 1. Solitude can be hard to discover 2it has been given up. In this respect,new technologies have3 our culture.

       The desire to be connected has brought solitude to a(n) 4 as we've known it. People have become so 5in the world of networks and connections that one can often be contacted 6they'd rather not be. Today we can talk, text, e­mail, chat and blog (写博客), not only from our 7, but from our mobile phones as well.

         Most developed nations have become 8on digital technology simply because they've grown accustomed to it, and atthis point not 9 it would make them an outsider. 10, many jobs and careers require people to be 11.From this point of view, technology has changed the culture of work. Being reachable might feel like a 12 to those who may not want to be ableto be contacted at all times.

 I suppose the positive side is that solitude is still possible for anyone who13 wants it. Computers can be shut 14andmobile phones can be turned off. The ability to be “connected” and “on” hasmany 15, as well asdisadvantages. Travelers have ended up 16on mountains, and mobilephones have saved countless lives. They can also make people feel 17and forced to answer unwanted calls or 18 to unwanted texts.

         Attitudes towards our connectedness as asociety 19across generations. Some find today's technology a gift.Others consider it a curse. Regardless of anyone's view on the subject, it'shard to imagine what life would be like20daily advancements intechnology.