To make OSPF area 4 totally stubby, the following command was issued on the ABR in router configuration mode: area 4 stub.Which two things need to be done to finish making area 4 a totally stubby area?（）

• A、Apply the area 4  stub command to all routers in the area
• B、On the ABR, use the area 4 stub command with the no - summary keyword
• C、On the ABR, specify a default cost for the area with the area default - cost command
• D、On the ABR, use the default - information originate  command to inject a default route into area 4
• E、Use the auto - cost command on each router in the area to automatically determine the cost to other OSPF areas