From the above excerpt the fact which best support Peter's opinion is that STUDENTS WHO PLAY AN INSTRUMENT GET BETTER GRADES THAN STUDENTS WHO DO NOT. This can be inferred from the passage: Peter considered playing an instrument a lot of fun; playing musical instruments is great for brain development. It helps the brain develop neurophysiological distinction which helps students distinguish between certain sounds that can aid in literacy.
Don't quote me on this, but it might be C
Paradoxes work by circularly falsifying the previous statement, and changing what the statement is asking.