During BGP configuration on a router that has peered with other BGP speakers, the BGP command aggregate-a ddress 172.32.0.0 255.255.252.0 is issued. However, the peers do not receive this aggregate network in BGP advertisements. Also, the router does not have this aggregate network in its BGP table. Which option indicates a possible reason this command did not cause the router to advertise the aggregate network to its peers?（）
- A Interface NULL 0 is likely shutdown.
- B The next hop IP address must be a loopback address.
- C The BGP command no auto - summary is missing.
- D The BGP command no synchronization is missing.
- E Subnets of 172.32.0.0/22 do not exist in the BGP table.
- F The IGP running on this router does not have network 172.32.0.0/22 installed.