For acceptable voice calls， the packet error rate should be less than（）%  

A. activity audit
B. administration
C. policy establishment
D. technology implementation

A. use ISL encapsulation
B. use 802.1q encapsulation
C. set ISL to desirable and auto with encapsulation negotiate to support ILS protocol negotiation
D. use VTP server mode to support dynamic propagation of VLAN information across the network 
E. set DTP to desirable and desirable with encapsulation negotiate to support DTP protocol negotiation.

A. for multiple ISDN connections
B. for modem concentrated dial-up connections
C. for a group of users in the same vicinity sharing a connection
D. for use by mobile users