There were a number of intelligent gentlemen at the party but it was Mr. Farrukh, an eminent scientist, who remained _ centre of attraction.

Explanation

The sentence should read:"There were a number of intelligent gentlemen at the party, but it was Mr. Farrukh, an eminent scientist, who remained the centre of attraction."The definite article "the" is used before "centre" because it refers to a specific, previously implied centre of attraction. The sentence implies that among the many intelligent gentlemen, Mr. Farrukh was the main focus of attention.