As shown in the figure, four MSR routers are connected via Ethernet and serial interfaces, and OSPF is running in the network at the same time. The area is divided as shown in the figure.

It is known that the OSPF Cost value of all interconnection links is the same, except that the link between RTB and RTC is PPP, the other interconnection links are all Ethernet. So ______ . (Multiple choice)

The command to configure the bridge priority of the switch SWA to 0 is ______.

A network connection is shown in the figure.

All interfaces of the four routers are configured with OSPF, and they are all running in OSPF area 23. All network segments can be connected to each other.
The OSPF Cost of the interconnection links between routers is shown in the figure. Then the correct description below is ______. (Multiple choice)

According to the definition of the OSI seven-layer reference model, _____ is responsible for providing flow control, checking the correctness of data transmission, and providing support for multiple upper-layer protocols. (Multiple choice)

In the command line, if the user wants to return to the previous view from the current view, they should use ______.