Explanation/Reference:
Exchange-specific cost
By default, Exchange uses the cost assigned to an IP site link for Active Directory replication purposes to compute a routing topology.

Route Mail Between Active Directory Sites: Exchange 2013 Help
NOT A C D
Need to introduce an exchange specific cost not change and AD cost
B
You need to recommend changes to the transport configurations to ensure that all email messages sent from the Detroit office are routed through EX2.
All of the Detroit Users have a mailbox hosted on EX2 currently (New York) After the planned changes all of Detroit mailboxes would be shifted to EX3. (Detroit) The office in New York and Detroit connect to the internet directly.
In order to change the transport configuration to ensure that all email messages sent from the Detroit office are routed through EX2 an exchange specific cost has to be implemented.
B is the only answer option which achieves this.
[A40]
1. Run the New-Mailbox cmdlet
2. Run the New-ManagementRole -Parent
MyContactInformation -Name Role1
3. Run the Remove-ManagementRoleEntry
Role1 Set-User command
4. Run the Add-ManagementRoleEntry Role1Set-User
-Parameters Office, Homephone
5. Run the New-RoleAssignmentPolicy -Name Policy1
-Roles MyBaseOptions, Role1,
MyVoiceMail, MyTextMessages, MyTeamMailboxes,
MyMarketPlaceApps, MyDistributionGroupMembership