In the sentence, 'None but the brave deserves the fair, the word 'but' is used…

Correct answer: A preposition

Explanation –

'But' in the sentence "None but the brave deserves the fair" means 'except', so it functions as a preposition indicating exception.

Rephrasing: "None except the brave deserves the fair."

• How to test: Try replacing 'but' with 'except'. If the sentence remains grammatical and the meaning is preserved, 'but' is acting as a preposition.

• Contrast: When 'but' joins clauses (e.g., 'I wanted to go, but I was tired'), it is a conjunction.

• Other uses: Depending on context, 'but' can also appear as an adverb (e.g., 'nothing but trouble') or, more rarely, as a noun; this sentence demonstrates the prepositional use.

Therefore, the correct choice is: A preposition.