题目

Spiderman is one of the most famous comic book heroes of all time. He was created by Stan Lee in 1963 and was first introduced to the world in the pages of Marvel comic books. Spiderman’s story is the story of Peter Parker, a child who lost his parents and lives with his aunt and uncle. Peter is a shy, quiet boy wearing glasses and has few friends. One day, on a high school class trip to a science lab, he gets bitten by a special spider. Soon Peter realizes he has amazing powers: he is as strong and quick as a spider and also has a type of sixth sense. He no longer needs his glasses 关于磁场和磁感线的描述，正确的说法是（　　）A．磁感线是一种假想曲线，实际并不存在B．磁场的方向就是通电导体在磁场中某点受磁场作用力的方向C．沿磁感线方向，磁场逐渐减弱D．在磁场强的地方同一通电导体受的安培力可能比在磁场弱的地方受的安培力小