Single best option: B

Reasoning: In a Class V (cervical) preparation the mesial and distal extent of the outline form is carried only far enough to eliminate decalcified or carious enamel/dentin; there are usually no proximal contacts to dictate the outline, and enamel-rod direction mainly affects the incisal/gingival walls. Hence the mesial and distal walls are determined by how far the carious lesion spreads on each side, i.e., by the presence and lateral extent of caries (Sturdevant’s Operative Dentistry 14th ed.; Hilton & Ferracane, 2016, PMID 27381913).