Question

every galaxy observed by human is redshifted. what does this tell us about the universe?
○ the universe is shrinking.
○ the universe is expanding.
○ the composition of galaxies makes them appear red.
○ there are aliens among us.

Explanation:

Redshift occurs when light - emitting objects (like galaxies) move away from an observer. According to Hubble's law, the greater the distance of a galaxy from us, the greater its redshift. This is consistent with the idea of an expanding universe. If the universe were shrinking, we would expect blueshifts (galaxies moving towards us). The composition of galaxies causing a red appearance is not related to redshift (which is a Doppler - like effect for light). And the statement about aliens has no scientific connection to redshift observations.

Answer:

The Universe is expanding.