磁场（magnetic field）

1、The magnetic compass magnets are acted

The magnetic compass magnets are acted on by the horizontal component of the Earth’s total magnetic force. This magnetic force is GREATEST at the（）.Anorth magnetic poleBsouth magnetic poleCmagnetic prime vertical meridianDmagnetic equator

2、、命令“joinwithatonewfor学号=a.学号fields学号，姓

、命令“joinwithatonewfor学号=a.学号fields学号，姓名，性别，a.数学，a.英语”中包含的关系运算有（）A连接、选择B连接、投影C选择、投影、连接D选择、投影

3、When placed in a magnetic field, which

When placed in a magnetic field, which of the materials listed will maintain the highest permeability?（）AGlassBBakeliteCSoft ironDAluminum

4、Field Test

Field Test

5、场field

场field

6、田间试验 field experiment

田间试验 field experiment