You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You create a Web page that has a GridView control named GridView1. The GridView1 control displays the data from a database named Region and a table named Location. You write the following code segment to populate the GridView1 control：   01 protected void Page_Load（object sender， EventArgs e）   02 {   03   string connstr；   04   05   SqlDependency.Start（connstr）；   06   using （SqlConnection connection =   07     new SqlConnection（connstr））   08   {   09     SqlCommand sqlcmd = new SqlCommand（）；   10     DateTime expires = DateTime.Now.AddMinutes（30）；   11     SqlCacheDependency dependency = new   12       SqlCacheDependency（"Region"， "Location"）；  13     Response.Cache.SetExpires（expires）；   14     Response.Cache.SetValidUntilExpires（true）；   15     Response.AddCacheDependency（dependency）；   16 ►  17     sqlcmd.Connection = connection；   18     GridView1.DataSource = sqlcmd.ExecuteReader（）；   19     GridView1.DataBind（）；   20   }   21 }  You need to ensure that the proxy servers can cache the content of the GridView1 control.  Which code segment should you insert at line 16？（）

• A、Response.Cache.SetCacheability(HttpCacheability.Private); 
• B、Response.Cache.SetCacheability(HttpCacheability.Public); 
• C、Response.Cache.SetCacheability(HttpCacheability.Server); 
• D、Response.Cache.SetCacheability(HttpCacheability.ServerAndPrivate);