What describes nails that have a rough appearance due to lengthwise ridges?

The correct choice is that nails with a rough appearance characterized by lengthwise ridges are described as "brittle nails." When nails are brittle, they may become ridged or develop an uneven surface, which can occur due to a variety of factors including dehydration, nutritional deficiencies, or underlying health conditions. These ridges run vertically along the nail and can contribute to an overall unhealthy appearance.

The choice referring to lentigens is unrelated, as lentigens are small, brown spots on the skin, not a nail condition. Callous pertains to thickened skin areas that develop due to friction or pressure, which does not apply to the nails specifically. Onychia is an inflammation of the nail matrix, which can lead to different nail deformities but is not specifically defined by roughness or ridges. Thus, understanding the characteristics of brittle nails is essential for recognizing and diagnosing nail conditions effectively.