Answer: A  

Reasoning: Shifting the facial/gingival height-of-contour toward the incisal third removes bulk in the cervical area (i.e., creates an under-contoured cervical profile). This encourages the gingival margin to rebound coronally and visually shortens the exposed clinical crown, so the tooth looks shorter. In contrast, moving the contour gingivally or widening the proximal line angles tends to lengthen or widen the apparent crown height. [Su et al., 2010, PMID 20664835; Kinsel & Capoferri 2008, PMID 18592717]