My question is simple; I am US Citizen and after 10 days abroad the immigration officer on airport start asking me different questions. I AM ASKING : -What they should ask and what not ? Is there any question I may refuse to answer ? For example :-How long you have been outside US (damn, good question but is on computer ???!!! )
US citizens usually do not face much scrutiny reentering the US. If they do ask you questions, just answer them truthfully if possible. If they ask you something that might give rise to criminality and you do not wish to incriminate yourself then, of course, you should not answer and ask for an attorney.
With the current climate of fear, the US is not only cautious of foreigners entering the US but also its' own citizens. If you are defensive or evasive in answering questions by the US immigration officer be prepared to spend more time getting on US soil and being asked more questions.