A is correct because you need to configure BGP multihop to enable redundancy for the EBGP peering between the two routers. BGP multihop is a feature that allows BGP peers to establish a session over multiple hops, instead of requiring them to be directly connected. By default, EBGP peers use a time-to-live (TTL) value of 1 for their packets, which means that they can only reach adjacent neighbors. However, if you configure BGP multihop with a higher TTL value, you can allow EBGP peers to communicate over multiple routers in between. This can provide redundancy in case of a link failure or a router failure between the EBGP peers.
B is correct because you need to configure loopback interface peering to enable redundancy for the EBGP peering between the two routers. Loopback interface peering is a technique that uses loopback interfaces as the source and destination addresses for BGP sessions, instead of physical interfaces. Loopback interfaces are virtual interfaces that are always up and reachable as long as the router is operational. By using loopback interface peering, you can avoid the dependency on a single physical interface or link for the BGP session, and use multiple paths to reach the loopback address of the peer. This can provide redundancy and load balancing for the EBGP peering.
C is correct because you need to configure routes for the peer loopback interface IP addresses to enable redundancy for the EBGP peering between the two routers. Routes for the peer loopback interface IP addresses are necessary to ensure that the routers can reach each other's loopback addresses over multiple hops. You can use static routes or dynamic routing protocols to advertise and learn the routes for the peer loopback interface IP addresses. Without these routes, the routers will not be able to establish or maintain the BGP session using their loopback interfaces.

B is correct because the loops do not exist is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. A loop in BGP means that a route has been advertised by the same AS more than once, which can cause routing instability and inefficiency. To prevent loops, BGP uses the AS-path attribute, which lists the AS numbers that a route has traversed from the origin to the destination. The receiving router checks the AS-path attribute of the received route and discards it if it finds its own AS number in the list. This way, BGP avoids accepting routes that contain loops.
C is correct because the next hop is reachable is one of the conditions that are verified by the receiving router to ensure that the received BGP route is valid. The next hop is the IP address of the next router that is used to forward packets to the destination network. The receiving router checks the next hop attribute of the received route and verifies that it has a valid route to reach it.
If the next hop is not reachable, the received route is not usable and is rejected by the receiving router. This way, BGP ensures that only feasible routes are accepted.

A is correct because generated routes require a contributing route. A contributing route is a route that matches the destination prefix of the generated route and has a valid next hop. A generated route is only installed in the routing table if there is at least one contributing route available. This ensures that the generated route is reachable and useful. If there is no contributing route, the generated route is not added to the routing table.
B is correct because generated routes show a next hop in the routing table. A generated route inherits the next hop of its primary contributing route, which is the most preferred route among all the contributing routes. The next hop of the generated route can be either an IP address or an interface name, depending on the type of the contributing route. The next hop of the generated route can also be modified by a routing policy.

The feature that enables an interface on an EX Series switch to receive both untagged traffic (from the computer) and tagged traffic (from the IP phone) is the voice VLAN. The voice VLAN feature in EX-series switches enables access ports to accept both data (untagged) and voice (tagged) traffic and separate that traffic into different VLANs. This allows the switch to differentiate between voice and data traffic, ensuring that voice traffic can be treated with a higher priority.