如图所示,甲、乙两小磁针放在一根条形磁铁上下附近正中间位置处,丙、丁两小磁针放在该条形磁铁左右附近位置处.甲、乙、丙、丁四个小磁针静止时,甲、乙两小磁针的N、S极如图所示.关于丙、丁两小磁针和条形磁铁a、b两端的极性,下列判断正确的是( )
A:丙小磁针左端是S极,丁小磁针左端是N极
B:丙小磁针左端是N极,丁小磁针左端是S极
C:丙小磁针左端是S极,丁小磁针左端也是S极
D:该条形磁铁a端是N极,b端是S极
I'm Peter. There are four people in my family. They are my father, my mother, my grandfather and me. I'm twelve. My birthday is on 15th March. My parents are both doctors. They help people. Their birthdays are both in May. My grandfather is old. He is sixty-five. His birthday is on 9th June. He likes reading. I like reading too. I want to be a teacher in the future. I want to teach Chinese in a school.
请用力的图示法在图中画出重为8牛的物体对水平地面的压力.