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.

Q: Sentence: 'Buffy looks at Xander .', Argument/Subject 1: 'buffy', Argument/Subject 2: 'xander'

A: look up at
****
Q: Sentence: 'XHTML provides the framework for future extensions of HTML and aims to replace HTML in the future .', Argument/Subject 1: 'html', Argument/Subject 2: 'xhtml'

A: be replace by
****
Q: Sentence: 'Former Federal Reserve chairman Alan Greenspan wrote in a recent Financial Times op-ed that " the current financial crisis in the United States is likely to be judged the most wrenching since the end of the Second World War . " Resident scholar Vincent Reinhart opened an AEI conference Monday noting that his recent encounter with a book about Nostradamus may be " an omen . "', Argument/Subject 1: 'greenspan', Argument/Subject 2: 'federal reserve'

A:
be chairman of
****