Your company has a main office and a branch office.The network contains two DNS servers named DNS1 and DNS2.DNS1 is located in the main office. DNS1 hosts a primary standard zone named contoso.com. The contoso.com zone is configured to use DNSSEC.DNS2 is located in the branch office. DNS2 is a caching-only DNS server. You need to ensure that client computers in the branch office can receive authoritative responses to queries for contoso.com if a WAN link fails. DNSSEC security must be maintained.What should you configure on DNS2 for contoso.com？（）

A. a conditional forwarder
B. a secondary zone
C. a zone delegation
D. an Active Directory-integrated stub zone