A Bluetooth device can be either a master or a slave and any of the devices within a （71） can be the master．There is only one master and there can be up to （72） 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 （73） 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 （74） mode before it can become active．Within a network, all （75） communications are prohibited.
空白处（72）应选择（）
A．7
B．15
C．63
D．255
缺失，
面浅龋、近中舌向倾斜、不松动，余留牙牙石Ⅱ度，左侧下颌隆凸明显、倒凹大，上颌牙基本正常。