Explanation A prerequisite for configuring Mobility Groups is "All controllers must be configured with the same virtual interface IP address". If all the controllers within a mobility group are not using the same virtual interface, inter-controller roaming may appear to work, but the handoff does not complete, and the client loses connectivity for a period of time. -> Answer B is correct. Reference: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/configguide/ b_cg85/mobility_groups.html