问题：

[单选]

A Windows Communication Foundation (WCF) client uses the following service contract.(Line numbers are included for reference only.)
01 [ServiceContract]
02 public interface IService
03 {
04 [OperationContract]
05 string Operation1();
06 [OperationContract]
07 string Operation2();
08 }
You need to ensure that all calls to Operation1 and Operation2 from the client are encrypted and signed. What should you do?（）

A . Set the ProtectionLevel property in line 01 to EncryptAndSign.
B . Set the ProtectionLevel property in line 04 and line 06 to Sign.
C . Add a SecurityCriticalAttribute ror each operation.
D . Add a SecunitySafeCriticalAttribute for each operation.