关于遗传物质的探索：

（一） R型肺炎双球菌菌体无多糖类的荚膜，是无毒性细菌；S型肺炎双球菌菌体有多糖类的荚膜，是有毒性细菌，使人患肺炎或使小鼠患败血症．科学家艾弗里及其同事利用肺炎双球菌来探究什么是遗传物质的问题．实验材料、用具：S型细菌、DNA水解酶、培养基、培养器等．

艾弗里等人先做了三组实验：

①S型细菌的蛋白质+R型活细菌R型菌落；

②S型细菌荚膜的多糖+R型活细菌R型菌落；

③S型细菌的DNA+R型活细菌R+S型菌落；

（1）艾里弗等人后来发现上述实验步骤并不严密，于是又做了第四组实验，请按照①②③中表达式写出第四组实验方法和结果：④____ 

（2）从上述实验可以得出结论____ 

（3）肺炎双球菌具有的细胞器是____ 

（4）肺炎双球菌与酵母菌在结构上的主要区别是：____ 

（二）做噬菌体侵染细菌实验时，用放射性同位素标记某个噬菌体和细菌的有关物质如下表．产生的100个子代噬菌体与亲代噬菌体的形状、大小完全一样．试回答：

（1）子代噬菌体中，只含有³²P的有____ 个，只含有³¹P的有____ 个，同时含有³²P和³¹P的有____ 个．

（2）子代噬菌体的蛋白质分子中，都没有____ 元素，由此说明____；子代噬菌体的蛋白质分子都含有____ 元素，这是因为____ 

（3）实验中用放射性同位素标记噬菌体时，选取³⁵S和³²P这两种同位素分别标记蛋白质和DNA，能否用¹⁴C和¹⁸O标记？____（能或不能）说明理由：____ 

下列物质：①硫；②铁；③碳；④蜡烛．它们在氧气中燃烧（用相应的序号填空）：发出明亮的蓝紫色火焰的是　____ ；产生带刺激性气味的气体是____ ；能生成黑色固体的是____ ；只产生无色无味的气体并能使澄清石灰变浑浊的是____ ；发出白光，放出热量，在瓶壁上有水雾出现的是____ ．

完形填空

　　Today some people call Amsterdam the “City of Bicycles” because it is a city which is flat and convenient(便利的) for bicycles.

       In the 1960s, a group of cycling fans    1   an idea. They believed that it would be better for everybody if only bicycles were allowed in the city centre. They were   2    that this would help to save energy, reduce pollution and provide free public transport. The group painted hundreds of bicycles    3    and placed them in public places around Amsterdam for people to use.    4   was allowed to take them and use them for short journeys, whether he was a local or a foreigner. Wherever someone finished a journey, they would    5   the bike there for someone else to use. The problem was that it didn't work.    6    took all the bicycles within weeks!

          7     , more than thirty years later, the “white bike” is back in town—this time with a computer chip(芯片) to    8   its every move! To take a bicycle, you have to put a special card inside. The new “white bike” is not white any more but is an unusual    9   with bright colors. The bikes are parked at special parking places and people who want to use them have to take them to another place that has enough room.

          There is already less traffic in central Amsterdam,    10    both locals and tourists have been using the white bikes. Thanks to the good ideas of lots of people, like the cycling fans in the 1960s, many people around the world have been enjoying city centre streets without cars for many years.