You have a Skype for Business Server 2015 infrastructure that consists of two sites. The sites are located in New York a

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You have a Skype for Business Server 2015 infrastructure that consists of two sites. The sites are located in New York and Rome. Each site has Enterprise Voice deployed and contains separate dial plans and voice policies.
You plan to deploy dial-in conferencing to both sites. In each site, you create a dedicated conferencing policy. You assign the conferencing policies to the respective users in each site. You create a dial-in conferencing access number.
When you attempt to assign a region to the number, you discover that the regions are unavailable.
You need to ensure that you can add a region to the dial-in conferencing access number.
What should you modify?

A. the meeting configuration settings
B. the dial plans
C. the conferencing policies
D. the voice policies