Your company has a main office and 15 branch offices. The company has a single Active Directory domain. All servers run Windows Server 2008 R2.You need to ensure that the VPN connections between the main office and the branch offices meet the following requirements: ?¤All data must be encrypted by using en-to-end encryption. ?¤The VPN connection must use compute-level authentication. ?¤User names and passwords cannot be used for authentication What should you do？（）

• A、Configure an IPsec connection to use tunnel mode and preshared key authentication.
• B、Configure a PPTP connection to use version 2 of the MS-CHAP v2 authentication.
• C、Configure a L2TP/IPsec connection to use the EAP-TLS authentication.
• D、Configure a L2TP/IPsec connection to use version 2 of the MS-CHAP v2 authentication.