Question

blueshift means what? *

redshift
blueshift

an object is moving away from you
an object is approaching you
an object is not moving
an object is blue

Explanation:

Blueshift occurs when an object is moving towards an observer. This causes the light waves to be compressed, resulting in a shift towards the blue end of the spectrum. In contrast, redshift happens when an object is moving away, stretching the light waves and shifting them towards the red end. The other options are incorrect: an object not moving would show no shift, and "an object is blue" misinterprets the term (it's about light wave shift, not the object's color).

Answer:

An object is approaching you