问题：

[单选]

You are developing a Windows Communication Foundation (WCF) service to replace an existing ASMX Web service.The WCF service contains the following code segment. (Line numbers are included for reference only.)
01 [ServiceContract()]
02
03 public interface IEmployeeService
04 {
05 [OperationContract()]
06 EmployeeInfo GetEmployeeInfo(int employeeID);
07
08 }
09
10 public class EmployeeService : IEmployeeService
11 {
12
13 public EmployeeInfo GetEmployeeInfo(int employeeID)
14 {
15 ...
16 }
17 }
18
19
20 public class EmployeeInfo
21 {
22 ...
23 public int EmployeeID { get; set; }
24 public string FirstName { get; set; }
25 public string LastName { get; set; }
26
27 }The existing Web service returns the EmployeelD as an attribute of the Employeelnfo element in the response XML.You need to ensure that applications can consume the service without code changes in the client.
What should you do?（）

A . Insert the following code at line 02. [DataContractFormat()] Insert the following code at line 22. [DataMember()]
B . Insert the following code at line 02. [XmlSerializerFormat()] Insert the following code at line 22. [XmlAtttibute()]
C . Insert the following code at line 09. [XmlSerializerFormat()] Insert the following code at line 22. [XmlAttribute()]
D . Insert the following code at line 19. [DataContractFormat()] Insert the following code at line 22. [DataMember()]