The simplest solution would be to store the ID in the command argument:
<asp:LinkButton ID="lnkSubmit" runat="server" CommandName="Submit" Text="Action" CommandArgument='<%# Eval("ID") %>' />
protected void GridView1_RowCommand(object Sender, GridViewCommandEventArgs e)
{
if (e.CommandName.Equals("Submit"))
{
string id = (string)e.CommandArgument;
Response.Redirect("InquiryReg.aspx?id=" + Server.UrlEncode(id));
}
}