C

When the holes in the sheet are punched too far apart, the dam has to stretch excessively across the embrasure; this leaves a gap through which the gingival papilla “pops” into the operating field, so the papilla protrudes beyond the rubber dam. Correct spacing prevents this problem, whereas holes punched too close together usually cause bunching of the dam rather than papillary show-through [Christensen, 1994, PMID 8294668].