The human eye is able to see objects at different distances with contrasting illuminations due to the accommodation of the eye, which is the correct answer. Accommodation refers to the ability of the eye to adjust its focal length to focus on objects at different distances. When an object is far away, the ciliary muscles in the eye relax, causing the lens to flatten and increase its focal length. This allows the eye to see distant objects clearly. On the other hand, when an object is close, the ciliary muscles contract, causing the lens to become thicker and increase its refractive power. This allows the eye to focus on nearby objects.

Option 1, far-sightedness, is not the correct answer because far-sightedness, also known as hyperopia, is a condition in which distant objects are seen more clearly than nearby objects due to a shorter eyeball or a less powerful lens.

Option 2, near-sightedness, is not the correct answer either. Near-sightedness, also known as myopia, is a condition where nearby objects appear clear, but distant objects appear blurry due to elongation of the eyeball or a too-strong lens.

Option 3, far-sightedness and nearsightedness, is also not the correct answer,