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
Buccolingual positioning of mandibular Canal can be assessed by: 
Select and explain. 
A. Horizontal 0 and -20 degree., B. Horizontal 0 and -15 degree., C. Vertical 0 and -20 degree., D. Vertical 0 and -15 degree.
C: Vertical 0 and -20 degree.
Answer: C: Vertical 0 and -20 degree. 
Explanation: “Periapical radiographs taken from two vertical angulations, 0° (parallel technique) and – (Minus) 20°, determine the buccolingual position of the canal”.
“Periapical radiographs taken from two Horizontal angulations, 0° (parallel technique) and – (Minus) 20°, may differentiate between buccal and lingual roots”.