单项选择题
A Bluetooth device can be either a master or a slave and any of the devices within a ___30___can be the master. There is only one master and there can be up to ___31___ 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 ___32___.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 ___33___ mode before it can become active. Within a network, all ___34___ communications are prohibited.
34（）
A. master-to-master
B. Master-to-slave
C. slave-to-slave
D. Slave-to-master