想一想，电磁铁的优点有什么。日常生活中，电磁铁应用在哪些地方。
电磁铁磁性有无，可用通断电来控制；电磁铁磁性强弱，可用改变电流大小来控制；电磁铁的极性变换，可用改变电流方向来实现。日常生活中应用于电铃、电话听筒等
如图，点A是直线l外一点，在l上取两点B，C，分别以A，C为圆心，BC，AB长为半径画弧，两弧交于点D，分别连接AB、AD、CD，则四边形ABCD一定是（ ）
阅读下列短文, 从每题所给的四个选项（A、B、C、D）中选出最佳选项。
Notice
No more beautiful season than spring, so school trips will be organized in three grades.
Enjoy your time and have fun!
Grade Date Destination
Junior 1 April 13 Songcheng, Hangzhou
Junior 2 April 14 Songcheng, Hangzhou
Junior 3 April 13 Zhouzhuang Ancient Town, Kunshan(in the southeast of Suzhou)
Price: RMB ￥115 (Songcheng) RMB ￥150 (Zhouzhuang)
Parking Place: Coaches for Kunshan Southern Gate
Coaches for Hangzhou Northern Gate
关于我国北方地区农业生产的叙述，错误的是（ ）
