[ابو بيشو]

He is the best surgeon of the hospital.
He is the best surgeon in the hospital.
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It is one of the best theatres of Spain.
It is one of the best theatres in Spain.
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The phrase that follows the best (+ noun) usually begins with in (NOT
of): 'one of the best restaurants in London', 'the best team in the league',
'some of the best students in the class'