You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You create an AJAX-enabled Web form by using the following code fragment：                           ...         When the updFirstPanel UpdatePanel control is updated， a dynamic client script is registered. You write the following code segment in the code-behind file of the Web form：   01 protected void Page_Load（object sender， EventArgs e）   02 {   03   if（IsPostBack）   04   {   05     string generatedScript = ScriptGenerator.GenerateScript（）；   06 ►  07   }   08 }    You need to ensure that the client-script code is registered only when an asynchronous postback is issued on the updFirstPanel UpdatePanel control.  Which code segment should you insert at line 06？ （）

• A、A
• B、B
• C、C
• D、D