The correct option is B Linguist
'Linguist' is a person skilled in foreign languages. Hence, option B is correct.
The word, 'bilingual' is an adjective which means 'speaking two languages fluently'. 'Philosopher' is a person engaged or learned in philosophy, especially as an academic discipline. 'Narrator' is a person who narrates something, especially a character who recounts the events of a novel or narrative poem.
As the meanings of the above three words, do not mean the same as 'one who knows many languages', options A, C and D are incorrect.