The correct choice is black line stain. Black line stain is a distinctive type of extrinsic dental stain that typically appears as a narrow band or line located at the gingival margin, often associated with the gingival third of the teeth. This stain is generally more prevalent in females, which aligns with the demographic noted in the question.
Black line stain is primarily composed of microorganisms and is often found in individuals who have good oral hygiene practices, although it may be mistakenly assumed to indicate poor dental care. The composition of this stain is thought to include iron, and it is usually more common in children and young adults, particularly in females, contributing to its recognition.
Understanding the characteristics of black line stain—its location, demographic associations, and the fact that it occurs despite good oral hygiene—provides a context for identifying this specific retentive stain among various other stains that may appear on teeth.