the presence of dark matter red shift of light from distant galaxies constant speed of light from every perspective emission of high-energy gamma rays by distant objects
I gave my students this multiple choice question: Which is evidence that the universe is expanding?

Only one answer is correct among these 4 choices:
- the presence of dark matter
- red shift of light from distant galaxies
- constant speed of light from every perspective
- emission of high-energy gamma rays by distant objects

Could you tell me which one is correct?

red shift of light from distant galaxies