Correct option is : (C) Achromatic combination
Chromatic aberration occurs when a lens fails to focus all colors to the same convergence point. This is typically due to the different refractive indices of the lens material for different wavelengths of light. To reduce chromatic aberration, an achromatic combination of lenses is often used. This combination typically consists of a convex lens made of crown glass and a concave lens made of flint glass.
The two lenses are designed to bring two wavelengths (usually red and blue) into focus at the same point, thus minimizing the color distortion.
