If you do not see the Correct Answer Indicator after adding it to your slide, check to make sure you have specified a correct answer.
Microsoft Office 2003
1. Select Tools => Settings
2. On the left side of Settings select the answer that was set as correct
3. Under Answer Settings confirm Answer Value is set as correct
Microsoft Ofice 2007 & 2010
1. Check Settings Pane on right to confirm an Answer Value is set as correct
Note: Setting a point value does not set an Answer Value as correct