người điều tra 
investigator [ người ] : man, person, people, individual, body
[ điều ] : (1) thing, matter, item; article (of penal code, constitution); (2) smoking pipe; (3) bird [=chim]
[ tra ] : (1) to consult, look up; (2) to fit in; (3) to add; (4) to apply
Most Common Compounds Set 1:
Most Common Compounds Set 2 :