Chromatic Aberration, the Inability of a Simple Lens to Focus

Multiple Choice

Chromatic aberration, the inability of a simple lens to focus all colors of light to the same focal point, is reduced in astronomical telescopes by

A) adding a carefully shaped mirror to the lens to produce a lens-mirror combination.
B) combining two lenses of different shape, made from the same kind of glass.
C) bending the lens in its mounting.
D) combining two lenses of different shape, made from different kinds of glass.