Why does a midi system have the widest range of frequencies out of trumpet, violin, piano, clarinet, pipe organ, kettle drum and a midi system. you get 15 points

Each of these instruments have a very wide range of notes because these are all treble instruments. Now, if you mean altogether, with a trumpet you can hit a very wide range of notes due to it having such a high octave, same with a violin, piano, clarinet, and organ. Kettle drums just have a very manipulable sound.
But remember it is a MIDI System, and you can adjust the frequency according to your desire; So, honestly, there is no straight answer for this, just how you desire the sound.

I could take an A4 note on a trumpet and stretch the sound waves out to sound like an A1 note just by bending it with a MIDI System. So, the possibilities are endless.