实验室提供如下的器材：电流表、电压表，滑动变阻器、定值电阻R、开关、电源各一个，导线若干．小强想通过以上的器材进行下列实验，你认为不可行的是（　　）

    When you are in England, you must be very careful in the streets because the traffic drives on the left. Before you cross a street, you must look to the right first and then left. If the traffic lights are red, the traffic must stop. Then the people on foot can cross the road.
    If the traffic lights are green, the traffic can go. People on foot mustn't cross. In the morning and in the evening when people go to or come from work, the streets are very busy. Traffic is most dangerous then.
    When you go by bus in England, you have to be careful, too. Always remember the traffic moves on the left. So you must be careful. Have a look first or you will go the wrong way.
   In many English cities, there are big buses with two floors. You can sit on the second floor. From there you can see the city very clearly. It's very interesting.

在宏观、微观和符号之间建立联系是化学学科的特点．