The usage of the indirect question root iu- is basically similar to the use of indirect questions in English.
Indirect questions are about knowledge and belief, so they are best expressed with clauses and cieg-, a root whose meaning includes mental models.
Example 5.4. Indirect Questions
Pa iupe hexu ofciegxe. Belief what+exist clause+part I+model+whole. I know what that is.
Pa fuaaiupe hexu ofciegxe. Belief person+what+exist clause+part I+model+whole. I know who that is.
Ili ofxe pehanpokigeiuxu hexu atciega hexu ofciegxe ep. Immediate I+whole smart+opposite+kind-of+what+part clause+part you+model+same clause+part I+model+whole not. However I+model+whole inference difference+kind-of+part clause+part. I don't know what kind of idiot you take me for, but I'm certain that I'm a different kind. (the Daily Whale, 23 April 2002)