题目内容：
A Bluetooth device can be either a master or a slave and any of the devices within a （ ）can be the master. There is only one master and there can be up to （ ） 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 （ ） 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 （ ） mode before it can become active. Within a network, all （请作答此空） communications are prohibited.
A.MASTER-TO-MASTER
B.MASTER-TO-SLAVE
C.SLAVE-TO-SLAVE
D.SLAVE-TO-MASTER
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答案解析：