Final answer:
The observed redshift in the light from distant galaxies suggests the universe is expanding, with galaxies moving away from us. This redshift is due to the stretching of space itself rather than the motion of the galaxies through space.
Step-by-step explanation:
Observed light from distant galaxies suggests that the universe is expanding. This is evidenced by a phenomenon known as redshift in the light emitted by these galaxies. The spectral lines are shifted toward the red end of the spectrum, implying that the galaxies are moving away from us. Edwin Hubble's observations in 1929 confirmed that the farther a galaxy is from us, the greater its redshift, which follows what is now known as Hubble's Law. This redshift occurs because the space through which the light travels is stretching, thereby increasing the wavelength of the light.
The correct answer to the student's question is A. The light from distant galaxies shows a redshift, indicating they are moving away from us. This observed redshift conveys a stretching of space and corroborates the theory that the universe is undergoing expansion. It is important to note that all galaxies except those in our local cluster display this redshift, reinforcing the concept of a uniformly expanding universe.