问题：

[单选]

You are the senior technician at Certkiller.com. You have been instructed to create a MicrosoftASP.NET application using Microsoft .NET Framework v3.5. 
You make use of ASP.NET AJAX to create a web form. In order to handle exception from
asynchronous postbacks you decide to write the client script code fragment below. You write thefollowing client-script code fragment to handle the exceptions thrown from asynchronouspostbacks. （The line numbers is included for reference purposes）
01 <script type="text/javascript">
02 function pageLoad（）
03 {
04  var pageMgr = Sys.WebForms.PageRequestManager.getInstance（）；
05
06 }
07
08 function errorHandler（sender， args）
09 {
10
11 }
12 </script> 
You receive an instruction from the network administrator to ensure that the application is able toexecute the criteria below：
* You need to ensure that the application makes use of a common client-script function namederrorHandler.
* The Label control with an ID named TestError should be updated with the error message.* The browser should not display any message box or Javascript error 
How can this be accomplished？（）

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