问题：

[单选]

You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. 
You create a login Web form by using the following code fragment. <asp：ScriptManager ID="ScriptManager1" runat="server" /> 
<asp：TextBox runat="server" ID="txtUser" Width="200px" /> 
<asp：TextBox runat="server" ID="txtPassword" Width="200px" /> 
<asp：Button runat="server" ID="btnLogin" Text="Login" OnClientClick="login（）； return false；" /> When a user clicks the btnLogin Button control， the login（） client-side script is called to authenticate the user. The credentials provided in the TextBox controls are used to call the client-side script. You also add the following client-script code fragment in the Web form. （Line numbers are included for 

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 - 151 - Test Information Co.， Ltd. All rights reserved. reference only.） 
01 <script type="text/javascript"> 
02 function login（） { 
03 var username = $get（’txtUser’）.value； 
04 var password = $get（’txtPassword’）.value； 
05 
06 // authentication logic. 
07 } 
08 function onLoginCompleted（validCredentials， userContext， 
09 methodName） 
10 { 
11 // notify user on authentication result. 
12 } 
13 
14 function onLoginFailed（error， userContext， methodName） 
15 { 
16 // notify user on authentication exception. 
17 } 
18 </script> 
The ASP.NET application is configured to use Forms Authentication. The ASP.NET AJAX authentication 
service is activated in the Web.config file. 
You need to ensure that the following workflow is maintained： 
&iexcl；¤On successful authentication， the onLoginCompleted clien-script function is called to notify the user. 
&iexcl；¤On failure of authentication， the onLoginFailed clien-script function is called to display an error message. 
Which code segment should you insert at line 06？（）

A . A
B . B
C . C
D . D