Explain why the aurora borealis, or northern lights, can be seen at the north pole but not at the equator.

At north pole the magnetic field strength is very high due to which charge particles enter with very high speed and the air get oxidized and when its excited electrons come back to ground state it releases the photons of different colors.

Now this phenomenon is possible only when magnetic field strength is good so near the north pole and south pole of earth this strong magnetic field exist which can exhibit the phenomenon of aurora borealis and since the magnetic field strength is less at equator so we can not see this phenomenon near equator.

there is no correct list among the choices you've provided.

the list might look something like this:

-- baby human

-- piccolo

-- flute

-- soprano singer

-- trumpet

-- tenor singer

-- trombone

-- baritone singer

-- baritone horn

-- bass singer

-- tuba

since i had to make up the list myself, i made it easy on myself, and i didn't try to shuffle the string instruments and woodwinds into it too.