You have an Exchange Server 2010 organization.The organization is authoritative for the domain contoso.com.You create a federated trust.You need to ensure that federated partners can automatically locate the Client Access servers in the organization. What should you create from an external DNS server？（）

• A、an A record for autodiscover.contoso.com
• B、an A record for FederatedSharing.contoso.com
• C、an SRV record for _autodiscover._TCP._msdcs.contoso.com
• D、an SRV record for _FederatedSharing._UDP._msdcs.contoso.com