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 high occlusal contact occurs in the balancing position between the lingual cusp of maxillary 1st molar and the buccal cusp of mandibular 1st molar. To eliminate this, which surface should be reduced? 
Select and explain. 
A. Lingual cusp of maxillary 1st molar and buccal cusp of mandibular 1st molar, B. Either lingual cusp of maxillary 1st molar or buccal cusp of mandibular 1st molar, C. Lingual cusp of maxillary 1st molar with milling paste at the time of denture  insertion, D. Lingual cusp of maxillary 1st molar in centric and occluding position
B: Either lingual cusp of maxillary 1st molar or buccal cusp of mandibular 1st molar
Answer: B: Either lingual cusp of maxillary 1st molar or buccal cusp of mandibular 1st molar 
Explanation: These are balancing side interferences and slopes of either of the involved cusp tips should be reduced.