A Bluetooth device can be either a master or a slave and any of the devices within a (1) can be the master. There is only one master and there can be up to (2) active slave devices at a time within a single network. In addition, a device may be a standby slave or a parked slave. There can be up to (3) parked slaves. If there are already maximum number of active slaves, then a parked slave must wait until one of the active slaves switches to (4) mode before it can become active. Within a network, all (5) communications are prohibited.
3（）
A．127
B．255
C．511
D．1023
g的加速度运动时，绳的拉力为
mg，则A对地面的压力为多大？