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
If the pulp of the single rooted canal is triangular in cross-section with the base of the triangle located facially and apex located lingually with the mesial arm longer than the distal, the tooth is most likely: 
Select and explain. 
A. Max. central incisor, B. Max. lateral incisor, C. Mand. second premolar, D. Mand. central incisor
A: Max. central incisor
Answer: A: Max. central incisor 
Explanation: SHAPE OF ACCESS CAVITY:
Maxillary Incisors - Rounded triangle with the apex towards cingulum.
Maxillary Canine - Ovoid labiolingually.
Maxillary Premolar - Ovoid in Buccolingual direction (Slot shaped).
Maxillary Molars - Triangle in the mesial half base towards buccal and apex towards palatal side.
Note if asked in exams:
           - Rhomboidal (1st choice) 
           - Rounded Triangle (2nd choice)
Modified Access Cavity in maxillary molars (to accommodate accessory orifice):
           - Clove leaf.
           - Shamrock preparation.
MANDIBULAR TEETH:
Mandibular Incisors - Narrow rounded triangle or ovoid.
Mandibular Canine - Ovoid / funnel shaped.
Mandibular Premolar - Ovoid buccolingually.
Mandibular Molars - Trapezoidal (1st choice)
                    - Rounded Triangle (2nd choice)