Concept:Lumbar vertebrae are built to bear more body weight than thoracic vertebrae.Explanation:The centrum is the weight-bearing body of a vertebra.Lumbar vertebrae support a greater load, so their centrum is thicker and more robust.Thoracic vertebrae are lighter because they also articulate with the ribs.They have costal facets for rib attachment, which lumbar vertebrae lack.Other differences exist, but the thicker centrum is the most distinctive feature of lumbar vertebrae.Answer:C. thicker centrum.