问题：
[单选] You are creating a Windows Communication Foundation （WCF） service to process orders. The data contract for the order is defined as follows. [DataContract] public class Order { [DataMember] public string CardHolderName { get； set； [DataMember] public string CreditCardNumber { get； set； } }You have the following requirements： "Enable the transmission of the contents of Order from the clients to the service. "Ensure that the contents of CreditCardNumber are not sent across the network in clear text. "Ensure that the contents of CreditCardNumber are accessible by the service to process the order. You need to implement the service to meet these requirements. What should you do？（） For interactive and self-paced preparation of exam 70-513， try our practice exams. Practice exams also include self assessment and reporting features!
A . Add a DataProtectionPermission attribute to the CreditCardNumber property and set the ProtectData property to true.
B . Convert the DataContract to a MessageContract and set the ProtectionLevel property to SignAndEncrypt.
C . Change the data type of CreditCardNumber from string to SecureString.
D . Implement the CreditCardNumber property getter and setter.
