2. What causes a repelling force?

If two magnetic south poles or two magnetic north poles are brought near each other, the magnetic force is repulsive and the magnets will push against each other in opposite directions. If opposite poles are brought near, it is attractive. But the fundamental origin of the magnetic field is moving charge.

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.