You are the systems engineer for Contoso， Ltd. The internal network consists of a Windows NT 4.0 domain. The company maintains a separate network that contains publicly accessible Web and mail servers. These Web and mail servers are members of a DNS domain named contoso.com. The contoso.com zone is hosted by a UNIX-based DNS server running BIND 4.8.1. Contoso， Ltd.， is planning to migrate to a Windows Server 2003 Active Directory domain-based network. The migration plan states that all client computers will be upgraded to Windows XP Professional and that all servers will be replaced with new computers running Windows Server 2003. The migration plan specifies the following requirements for DNS in the new environment： • Active Directory data must not be accessible from the Internet. • The DNS namespace must be contiguous to minimize confusion for users and administrators. • Users must be able to connect to resources in the contoso.com domain. • Users must be able to connect to resources located on the Internet. • The existing UNIX-based DNS server will continue to host the contoso.com domain. • The existing UNIX-based DNS server cannot be upgraded or replaced. You plan to install a Windows Server 2003 DNS server on the internal network. You need to configure this Windows-based DNS server to meet the requirements specified in the migration plan. What should you do？ （）

A. Create a primary zone named ad.contoso.com on your Windows-based DNS server. Create a delegation record for the new zone on the UNIX-based DNS server. Configure forwarders on your Windows-based DNS server.
B. Create a primary zone named ad.contoso.com on the UNIX-based DNS server. Create a secondary zone on your Windows-based DNS server for the ad.contoso.com domain.
Create a primary zone named contoso-ad.com on your Windows-based DNS server. Create a secondary zone on the UNIX-based DNS server for the contoso-ad.com domain.
D. Create a primary zone named contoso-ad.com on the UNIX-based DNS server. Create a stub zone on the Windows-based DNS server for the contoso-ad.com domain. Configure conditional forwarders on your Windows-based DNS server for the contoso-ad.com and contoso.com domains.