The intended answer is the seatbelt mark: the sources stress that seatbelts cause characteristic abdominal and thoracic injuries (mesenteric tear, so-called "seatbelt syndrome", and duodenal/pancreatic injury from compression against the spine).

• However, the option says "upper chest", and a deep stab wound to the right flank is also an obvious risk for abdominal/retroperitoneal injury. The sources do not address flank stabs, so C is a reasonable alternative.