While editing answers to questions of type multiple choice. It was not possible to add answers.
There were 2 save buttons (Button_11), one of which I would've expected to be a button to add an answer (Button_14). 
Tried and tested on my system at least.

Index: CATS/classes/Answer.class.php
===================================================================
--- CATS/classes/Answer.class.php	(revision 1641)
+++ CATS/classes/Answer.class.php	(working copy)
@@ -273,7 +273,7 @@
     }    
     echo "<tr>";
     echo"<td class='leftColumn'></td>";
-    echo"<td class='Button_row'><input name='submit' class='Button_rightColumn' type='submit' value='".Button_11."'/> "; 
+    echo"<td class='Button_row'><input name='addAnsw' class='Button_rightColumn' type='submit' value='".Button_14."'/> "; 
     echo"<input type='submit' class='Button' name='minAnsw' value='".Button_15."'/></td>";  
     echo"</tr>";    
     echo "<tr>";