Your network consists of a single Active Directory domain. The domain contains a server named Server1 that runs Windows Server 2008 R2. All client computers run Windows 7. All computers are members of the Active Directory domain. You assign the Secure Server (Require Security) IPsec policy to Server1 by using a Group Policy object (GPO). Users report that they fail to connect to Server1. You need to ensure that users can connect to Server1. All connections to Server1 must be encrypted. What should you do？（）

A. Restart the IPsec Policy Agent service on Server1.
B. Assign the Client (Respond Only) IPsec policy to Server1.
C. Assign the Server (Request Security) IPsec policy to Server1.
D. Assign the Client (Respond Only) IPsec policy to all client computers.