In the sentence, 'None but the brave deserve the fair, the word 'but' is used as:

Question

Question

This question was previously asked in

IB ACIO Grade-II Official Paper-I (Held On: 22 Feb, 2015)

Answer 1

The correct answer is Option 2 i.e. A preposition.

Key Points

When but is used as a preposition it means the same as except.
In the above sentence but denotes an exception i.e nobody except those who are brave deserves the fair.
Since but means except when it is used as a preposition, the correct answer is Option 2.

Additional Information

When but comes in a sentence depending upon how it's used it can be a conjunction, a preposition, an adverb, or a noun.
Different uses of but:

Parts of Speech	Meaning and Use
As a Conjunction	Used to introduce a phrase or clause contrasting with what is already been mentioned. Example: He stumbled but didn't fall. Used to indicate the impossibility of anything other than what is being stated. Example: One cannot but sympathize.
As a Preposition	Takes the meaning except, apart from, other than. Example: We were never anything but poor.
As an Adverb	Takes the meaning no more than, only. Example: He is but a shadow of his former self.
As a Noun	Used as an argument against something, as an objection. Example: "No buts - just get out of here."

Here we see that but takes the meaning of except only when used as a preposition, hence Option 2 is the correct answer.