如图所示，在同一平面上有a、b、c三根等间距平行放置的长直导线，依次载有电流强度为1A、2A、3A的电流，电流方向如图，则（ ）
A．导线a所受的安培力方向向左
B．导线b所受的安培力方向向右
C．导线c所受的安培力方向向右
D．由于不能判断导线c所在位置的磁场方向，所以导线c受的安培力方向也不能判断
根据右手螺旋定则可判断电流周围的磁场方向，根据左手定则可判断通电导体在磁场中的受力方向，并可知同向电流的通电导体相互吸引，反向电流的通电导体相互排斥．再由直线电流的磁场与电流本身的大小和场点到电流中心的距离有关，可判断AB正确．
故选AB
阅读短文，根据短文内容，从短文后得选项中选出能填入空白处的最佳选项。选项中有一项为多余选项。（共8分，每小题2分） Bill Gates is a very important person in the computer industry. He has been chief officer of Microsoft Company for several years. He is also the richest person in the United States. How did he do it? He learned a lot from his parents. While Bill was going to school, his father went to college, got a degree, and became a successful lawyer. 1 . His mother was a very busy teacher, but she also loved going to parties. From this, he learned something else: if you want to work hard and play hard, you have to make a schedule. 2 . While most of his friends were playing, Bill read all of the World Book Encyclopedia and finished it when he was 8 years old. 3 . He used to play a lot of sports — swimming， water-skiing, tennis. When Bill got older, he spent more and more time working and playing on a computer. Before he was twenty, Bill developed the world’s first computer language for the personal computer. 4 . He thought that every home was going to have a computer, and every computer would need software — his software. He said, “ I’m going to make my first million dollars on software by the time I’m 25.” And he did!
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