问题：

[单选] You need to design an administrative model that meets all business and technical requirements. What should you do？（）

A . Place the mailboxes for each region on a separate server. Create an administrative group for each region. Assign each regional technician Exchange Full Administrator permission over that region’s administrative groups. Assign the main office IT staff Exchange Full Administrator permission over each administrative group.
B . Place the mailboxes for each region on a separate server. Create an administrative group for each region. Assign each regional technician Exchange Full Administrator permission over all administrative groups. Assign the main office IT staff Exchange Full Administrator permission over each administrative group
C . Place the mailboxes from multiple regions on each server. Create an administrative group for each server. Assign each regional technician Exchange Full Administrator permission over the administrative groups that contain servers that hold mailboxes for that region. Assign the main office IT staff Exchange Full Administrator permission over each administrative group
D . Place the mailboxes from multiple regions on each server. Create a single administrative group for all servers. Assign each regional technician and the main office IT Staff Exchange Full Administrator permission over the administrative grou