A Windows Communication Foundation (WCF) application uses the following data contract.
You need to ensure that the following XML segment is generated when the data contract is
serialized. Which code segment should you use?

A.
[DataMember(EmitDefaultValue = false)] public string firstName = null;
[DataMember(EmitDefaultValue = false)] public string lastName = null;
[DataMember(EmitDefaultValue = true)] public int age = -1; [DataMember(EmitDefaultValue
= false)] public int ID = 999999999;

B.
[DataMember(EmitDefaultValue = true)] public string firstName;

[DataMember(EmitDefaultValue = true)] public string lastName;
[DataMember(EmitDefaultValue = false)] public int age = -1;
[DataMember(EmitDefaultValue = false)] public int ID = 999999999;

C.
[DataMember] public string firstName; [DataMember] public string lastName;
[DataMember(EmitDefaultValue = true)] public int age = 0 ; [DataMember(EmitDefaultValue
= true)] public int ID = 999999999;

D.
[DataMember] public string firstName = null; [DataMember] public string lastName = null;
[DataMember(EmitDefaultValue = false)] public int age = 0; [DataMember(EmitDefaultValue
= false)] public int ID = 999999999;