同学们为了比较锌、铁、铜三种金属的活动性，仅用组内物质就能达到目的是（ ）
①Zn、Fe、Cu、稀硫酸 ②Fe、ZnSO4溶液、CuSO4溶液
③Zn、FeSO4溶液、CuSO4溶液 ④Zn、Cu、FeSO4溶液．
A．只有④
B．②和③
C．①②④
D．①②③④
①锌、铁能和稀硫酸反应，铜不能和硫酸反应，说明锌、铁的活泼性大于铜的，但无法知道锌、铁的活泼性，所以①不能达到目的；
②铁和硫酸锌不反应，说明铁的活泼性小于锌的，铁和硫酸铜反应，说明铁的活泼性大于铜的，但无法比较锌和铜的活泼性，所以②不能达到目的；
③锌分别能把FeSO4溶液、CuSO4溶液中的铁、铜置换出来，但无法比较铁和铜的活泼性，所以③不能达到目的；
④锌能把FeSO4溶液中的铁置换出来，说明锌的活泼性大于铁的，铜置换不出FeSO4溶液中的铁，说明铁的活泼性大于铜的，这样就能三种金属的活泼性，即锌＞铁＞铜，所以④能达到目的；
故选A．
What do you usually use your cellphone for? Calling friends or sending them text messages? As technology develops，nowadays cellphones can do much more than that．They have become all-in-one cell-phones. A typical example is Apple’s phone.The touch-screen cellphone plays music，connects to the Web，sends emails and takes photos. More than 1 million Apple’s phones have been sold since it was sold in June. “Today’s young people enjoy using all kinds of digital functions，such as those of a music player，a camera and even a computer. An all-in-one cellphone is easy to carry. That is the goal of developing a technology to make our lives more convenient，simple and relaxed，said Professor Ding Shouqian at Nankai University． However, the all-in-one cellphones come with some problems. Users have complained that they are too complicated to use them, and that their battery life is too short. Cellphone producers say that they are working hard to make their phones even better. It is very convenient to use it. “We are trying to make the cellphones in a way that people can quickly move from phoning to taking pictures to listening to music, said Alastair Curtis, Nokia’s chief designer.“If you look at the Nokia 3250 model, it has a twisting(转动) bottom. So you twist it half a turn，and it’s in camera mode. You twist it another 90 degrees, and it’s in music player mode．”Japanese companies such as Toshiba and Fujitsu are also working to develop a new kind of battery for cellphones． If all the problems are solved in the future, all-in-one phones will change our lives for the better.
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