题型:问答题 简答题 Laura _____ in this school since she came to China. [ ]A. is studying B. was studying C. will study D. has studied 查看答案
题型:问答题 简答题 有关磁场的物理概念,下列说法中正确的是( )A.磁感应的强度是描述磁场强弱的物理量,是矢量B.磁感应强度的方向跟探测磁场的电流的方向无关C.一小段通电导线在某处不受磁场力,该处磁感应强度一定为零D.一小段通电导线所受磁场力的方向就是磁场方向 查看答案