过圆内的一点（非圆心）有____条直径．
The team will move a speed of 15 kilometers per hour, and have a short break every 2 hours. During the break they will tell stories_______ English.
求证：BC=3AD．
如图所示，小磁针甲、乙处于静止状态．根据标出的磁感线方向，可以判断出（ ）
可归为一类加以回收利用。它们属于()
