This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
A narrow continuous line of brown dots which follow contour of gingival margin of posterior teeth in children is known as: 
Select and explain. 
A. Burtonian line, B. Mesenteric line, C. Neonatal line, D. Developmental line
B: Mesenteric line
Answer: B: Mesenteric line 
Explanation: A black strain in the form of a fine line adjacent to the free gingival margin, which is not related to smoking, has been called metabolic strain and “mesenteric line.”
This stain may occur as a broad thin black line following the contour of the free gingival margin onto the interproximal surface of the teeth.