Among the following OSPF protocol states, ______ belong to the stable state.

Regarding the Stub area and NSSA area of the OSPF protocol, the following statements are incorrect: _______

The role of IP Internal ReachabilitInformation CLV in IS-IS packets is ______.

Among the following types of LSAs, the ones allowed in the backbone area are _________

In the topology shown in the figure, the following configurations are performed on RTA, RTB, RTC and RTD respectively:
RTA-LoopBack0] ip address 1.1.1.1 255.255.255.255
RTA]ospf 1
RTA-ospf-1]area 1
RTA-ospf-1-area-0.0.0.1]network 10.0.0.0 0.0.0.255
RTA-ospf-1]import-route direct
RTB-LoopBack0] ip address 2.2.2.2 255.255.255.255
RTB]ospf 1
RTB-ospf-1]area 1
RTB-ospf-1-area-0.0.0.1]network 10.0.0.0 0.0.0.255
RTB-ospf-1-area-0.0.0.1]area 0
RTB-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0
RTB-ospf-1-area-0.0.0.0]network 20.0.0.0 0.0.0.255
RTC-LoopBack0] ip address 3.3.3.3 255.255.255.255
RTC]ospf 1
RTC-ospf-1]area 0
RTC-ospf-1-area-0.0.0.0]network 20.0.0.0 0.0.0.255
RTC-ospf-1-area-0.0.0.0]area 2
RTC-ospf-1-area-0.0.0.2]nssa
RTC-ospf-1-area-0.0.0.2]network 30.0.0.0 0.0.0.255
RTC-ospf-1-area-0.0.0.2]network 3.3.3.3 0.0.0.0
RTD-LoopBack0] ip address 4.4.4.4 255.255.255.255
RTD]ospf 1
RTD-ospf-1]area 2
RTD-ospf-1-area-0.0.0.2]network 30.0.0.0 0.0.0.255
RTD-ospf-1-area-0.0.0.2]nssa
RTD-ospf-1]import-route direct
Which of the following routes may exist in the RTD routing table ______.