Saxophones produce sound by using the player's flow of air and creating an oscillating motion with the reed acting as an oscillating valve.<span> The reed and the resonances that are present within the air inside of the instrument produces a vibrating and radiating sound out of the holes as well as the belly of the instrument.</span>
I think it would be d if I'm not mistaken
The passage describes the Author's impression of students participating in the "Upward Bound" program and it is generally favourable towards the program, without giving a more specific reason for this favourable opinion, it's more the author's personal impression.
Thus, we could say that the author has a positive bias towards the program.
