You are implementing an ASP.NET application that includes a page named TestPage.aspx. TestPage.aspx uses a master page named TestMaster.master.You add the following code to the TestPage.aspx code-behind file to read a TestMaster.master public property named CityName. Protected Sub Page_Load（ByVal sender As Object，ByVal e As System.EventArgs） Handles Me.LoadDim s As String = Master.CityNameEnd Sub  You need to ensure that TestPage.aspx can access the CityName property. What should you do？（）

A.Add the following directive to TestPage.aspx. <%@ MasterType VirtualPath="~/TestMaster.master" %> 
B.Add the following directive to TestPage.aspx. <%@ PreviousPageType VirtualPath="~/TestMaster.master" %> 
C.Set the Strict attribute in the @ Master directive of the TestMaster.master page to true. 
D.Set the Explicit attribute in the @ Master directive of the TestMaster.master page to true.