题目

With more forests being destroyed, huge quantities of good earth _________ each year． A．is washing away                                         B．is being washed away C．are being washed away                               D．are washing away 答案：C于雯同学想自制一根小磁针，采取了如图所示的摩擦方法，则钢针被磁化以后，下列说法中正确的是 [　　] A．A端为N极，B端为S极 B．A端为S极，B端为N极 C．A端可能为N极，也可能为S极． D．以上的三种情况都有可能