Your network contains an Active Directory forest. All domain controllers run Windows Server 2008 R2  and are configured as DNS servers. You have an Active Directory-integrated zone for contoso.com.   You have a UNIX-based DNS server.   You need to configure your Windows Server 2008 R2 environment to allow zone transfers of the  contoso.com zone to the UNIX-based DNS server.  What should you do in the DNS Manager console（）

• A、Disable recursion.
• B、Create a stub zone.
• C、Create a secondary zone.
• D、Enable BIND secondaries.