Compiling and Linking GTK 3 with C project on Ubuntu

I believe this is not a duplicate question, I have seen all questions/answers before I post this question. I think I have a different situation here.

I use Ubuntu 12.04 and downloaded GTK 2 and 3. I have copied a simple GTK source code from GNOME's website. But when I use this command in terminal:

gcc `pkg-config --cflags --libs gtk+-3.0`  hello.c -o hello

I get this:

hello.c:(.text+0x17): undefined reference to `gtk_init'
hello.c:(.text+0x23): undefined reference to `gtk_window_new'
hello.c:(.text+0x47): undefined reference to `gtk_main_quit'
hello.c:(.text+0x5b): undefined reference to `g_signal_connect_data'
hello.c:(.text+0x67): undefined reference to `gtk_widget_show'
hello.c:(.text+0x6c): undefined reference to `gtk_main'

here is my code:

#include <gtk/gtk.h>

int
main (int   argc,
char *argv[])
{
  GtkWidget *window;

  gtk_init (&argc, &argv);

  window = gtk_window_new (GTK_WINDOW_TOPLEVEL);

  g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL);

  gtk_widget_show (window);

  gtk_main ();

  return 0;
}

I'm not sure if errors appear because I have two versions of GTK+ or what. I'm extremely newbie in Applications Development in Ubuntu/Linux.