You are unable to telnet to a router at address 203.125.12.1 from a workstation with the IP address 203.125.12.23. You suspect that there is a problem with your protocol stack. Which of the following actions is most likely to confirm your diagnosis?（）

A. in order to optimize the path that frames take from source to destination
B. to increase the priority so a designated port will become a root port
C. to increase the BID, so the switch is more likely to become root bridge
D. in order to allow VLANs to be sent from one switch to another across a single link
E. to force a given switch to become an STP server

A. designated ports.
B. duplex operating mode.
C. fast mode ports.
D. root bridge.
E. root ports.
F. BDPU priority.