Which of the following is a sign of infection in nails?

A sign of infection in nails is indicated by a color change or swelling. When nails become infected, the body's immune response causes inflammation, which often results in redness or discoloration around the affected area. This can manifest as a darker or altered color of the nail or surrounding skin. Swelling is another critical indicator, as inflamed tissue often expands due to the accumulation of fluid as part of the immune response.

In contrast, dryness may suggest dehydration or environmental damage rather than infection. Lengthening of the nail is typically a normal part of nail growth, while ridge formation might indicate other issues such as nutritional deficiencies or trauma but is not specifically a sign of infection. The presence of color change and swelling makes it a definitive sign that an infection could be present, distinguishing it from other nail conditions.