The diagrams below each show the motion of a distant star relative to earth (not to scale). the red arrows indicate the speed and direction of the star’s motion: longer arrows mean faster speed. rank the stars based on the doppler shift that we would detect on earth, from largest blueshift, through no shift, to largest redshift.

d) the number of neutrons plus the number of protons

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.