Which factor makes a user a poor choice to be included in the pilot group9

You have an on-premises Exchange organization. The organization plans to migrate to Office 365 You need to identify a group of users to designate as the pilot group
Which factor makes a user a poor choice to be included in the pilot group9
A. users who use Android devices
B. users who are delegates for multiple mailboxes
C. users who need access to public folders on Exchange 2007 servers
D. users who receive fewer than 25 email messages per day