Make visible on drop down menu selection??

This might seem simple, but I am looking to make certain objects on my asp.net page visible when a specific item from a drop down menu on the same page is selected. I am trying to do this on a page with no code behind aspx.cs page. How do I go about this? 
<p> Select your response type:<asp:DropDownList ID="responseDrpDwn" runat="server"> <asp:ListItem>--Please Select--</asp:ListItem> <asp:ListItem>Text</asp:ListItem> <asp:ListItem>DropDown</asp:ListItem> <asp:ListItem>RadioButton</asp:ListItem> </asp:DropDownList> <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="responseDrpDwn" ErrorMessage="Please select a response type" InitialValue="--Please Select-- ...