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
According to ADA specification of toothbrush width of brush head should be: 
Select and explain. 
A. 5/8-3/8inches., B. 5/16-3/8inches., C. 5/8-3/16inches., D. 5/16-3/16inches.
B: 5/16-3/8inches.
Answer: B: 5/16-3/8inches. 
Explanation: Length of brush head: 1-1.25 inches.
Width of brush head: 5/16-3/2 inches.
Bristles: 2-4 rows.
Tufts in a row: 5-12 tufts