Detailed Instructions: Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.
Problem:Sentence: 'Rep. Rahm Emanuel , D-Ill . , officially announced his resignation from Congress today to become President-elect Obama 's chief of staff , seeming to close the door on any chance of making a quick return to his old job , in case he has second thoughts .', Argument/Subject 1: 'rahm emanuel', Argument/Subject 2: 'staff'
Solution:
be chief of