Final answer:
Ringed hair is the correct answer, referring to the condition with alternating bands of gray and dark hair along the hair shaft.
Step-by-step explanation:
The condition where alternating bands of gray and dark hair exist is known as ringed hair. Ringed hair, or canities circinata, is a rare and unique hair pigmentation pattern where there are alternating bands of light and dark color along the length of the hair shaft. This condition can be congenital or acquired, and although it's not harmful, it can be a cosmetic concern for some individuals. It's different from matting, which involves tangled hair, canities, which is the general greying of hair due to aging or stress, and monilethrix, a condition characterized by beaded hair strands.