z三轴之矩为（）Amx(F)=–P，my(F)=–P，mz(F)=.PBmx(F)=P，my(F)=，mz(F)=–.PCmx(F)=–P，my(F)=P，mz(F)=Dmx(F)=P，my(F)=P，mz(F)=–.P