Answer:It should be the same on all routers in the domain.
Explanation: OSPFv3( Open Shortest Path First routing protocol) is the protocol that is used for working with Internet protocol version 6(IPv6). It contains the reference bandwidth that is the bandwidth containing the value in Mbps.It can be set by the user itself and does require that all the router have same reference bandwidth
Other options are incorrect because reference bandwidth does not avoid router to adjust the bandwidth, it goes to 100 Mbps value by default and does not increase the link's speed.