Which of the following methods can correct spherical aberration?

Blocking light rays from marginal areas of the lens effectively corrects spherical aberration because this optical distortion occurs when rays of light that strike a lens near its edge focus differently than those that strike near the center. By restricting the light that enters from the peripheral regions of the lens, the overall image quality is improved because it minimizes the number of aberrant rays that contribute to the distortion. This technique enhances the focus and clarity of the image produced by the optical system, thereby addressing the main issue caused by spherical aberration.

The remaining methods involve choices that do not directly address the core problem of spherical aberration as effectively. For instance, using only convex or concave lenses may help in other optical scenarios but does not alleviate the focus inconsistency caused by spherical aberration. Applying an anti-reflective coating might reduce reflections and improve light transmission but does not specifically address the refraction discrepancies that lead to spherical aberration. Thus, blocking marginal light rays offers the most direct solution to correct this particular optical issue.