Why Are the Gravitational Lens Image Arcs of a Distant

Multiple Choice

Why are the gravitational lens image arcs of a distant galaxy photographed around the center of a cluster of galaxies significantly more blue in color than the cluster galaxies themselves?

A) The gravitational lensing also produces differential refraction, which renders the outer arcs blue and the inner ones, which are among the nearby galaxies, red, like an atmospheric halo around the Sun.
B) We are seeing a more distant galaxy at an earlier stage in its evolution, and it is intrinsically more blue on account of star formation in galaxies early in the life of the universe.
C) We are seeing the more distant galaxy at an earlier stage in its evolution when the Hubble motion had not redshifted its spectrum as much as for nearer, and hence, later galaxies.
D) The lensing process shifts light toward the blue as predicted by general relativity.