From the given sentence, extract the phrase (often noun or verb) that carries the given relationship. The generated phrase should be present in the sentence.

[EX Q]: Given Relationship: 'be city of', Sentence: 'Lahore is Pakistan 's second largest city and the capital of the northeastern province of Punjab .'
[EX A]: city

[EX Q]: Given Relationship: 'be chairman of', Sentence: 'Alan Greenspan , Chairman of the Board of Governors of the Federal Reserve System , gave the conference keynote address .'
[EX A]: Chairman

[EX Q]: Given Relationship: 'be mayor of', Sentence: 'London 's mayor Boris Johnson launched a furious verbal attack on Labour MP Keith Vaz , it is claimed .'
[EX A]:
mayor