Drupal 7: Main menu not displaying child elements

In my main menu, I have primary links and child links. The primary links are printing just fine. However, when I make a child element (by either dragging it to the right or selecting a p开发者_如何学运维arent link), they aren't displayed in the menu at all. I can create a new menu, and the child elements display correctly. I also ensured that 'Show as Expanded' was selected. Are child 'Main Menu' elements not suppose to show up?

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All levels/childs of the menu stucture should be set in one menu tree (Main Menu in this case).

Now go to admin/structure/menu/settings and set your Main Menu to both Source for the Main links and Source for the Secondary links.

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Which theme are you using? If you using Bartik then that is your problem as the Bartik theme doesn't support drop down menus. See here http://drupal.org/node/1508652 The link includes a work-around