Answer: B

Reasoning: The primary mandibular second molar has three buccal cusps (mesiobuccal, distobuccal and distal) that are almost equal in height and bulk; the two lingual cusps (mesiolingual and distolingual) are also nearly equal to each other but are slightly shorter than the buccal cusps. Consequently, the statement that “all buccal cusps are of the same size > all lingual cusps are of the same size” is correct, whereas claims that the ML or DB cusp is the largest are not supported by morphometric studies of this tooth [Peretz & Smith 1993, PMID 8240081].