Refer to the exhibits. Router B should advertise the network connected to the E0/0/0 interface to router A and block all other network advertisements. The IP routing table on router A indicates that it is not receiving this prefix from router B.
What is the probable cause of the problem?

Correct Answer: A
Explanation/Reference:
Explanation
This is an unclear question. The question says Router B should advertise the network connected to the E0/0/0 interface to router A and block all other network advertisements. The IP routing table on router A indicates that it is not receiving this prefix from router B.
That means the network 192.168.3.16/28 (including the IP 192.168.3.21/28) is not received on router A -> A is the most suitable answer.
Note: Distribute list are used to filter routing updates and they are based on access lists.