Question

In which sentence is the word but used as a preposition?

A. Children should be seen but not heard.
B. We would like to visit the Grand Canyon, but our vacation time is up.
C. None but the brave shall enter in.
D. John liked baseball but not football.

Answer 1

for me B is the most appropriate answer

Answer 2

The sentence in which the word but is used as a preposition is C) None but the brave shall enter in.
This is true because the word but can be replaced with the preposition except, which means it is also a preposition.
In the rest of the sentences, but is used as a conjunction.