问题：

[单选]

Certkiller.com has hired you as a network administrator for their network. You are in the process ofcreating an ASP.NET application using .NET Framework v3.5. The newly created applicationcontains a DataSourceControl. 
This control is named KingCatagory. This control is bound to a Microsoft SQL Server 2005 table.The primary key of this table is the CatName column. In the FormView control you write thefollowing code. （The line numbers is included for reference purposes）
1 <tr>
2 <td align="right"><b>Category：</b></td>
3 <td><asp：DropDownList ID="DropDownList1" Runat="server"
4
5 DataSourceID="ds1" DataTextField="CatName" DataValueField="CatID" />
9 </td>
10 </tr> 
You receive an instruction frommanagement to make sure that modifications made to the CatIDfield can be written to the database. You thus need to determine the appropriate code fragmentthat needs to be added at line 4. 
What should you identify？（）

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