Which of the Following Bony Defects Has a Lesser Chance

Which of the following bony defects has a lesser chance of regeneration with a bone graft or bone replacement material?

A) One-wall infrabony on the maxillary first premolar
B) Three-wall infrabony on the mandibular second molar
C) Class II buccal furcation of mandibular first molar
D) Class II buccal furcation on the mandibular second molar