The vertebral column, or spine, consists of a total of 33 vertebrae in infants, but as a person matures into adulthood, some of these bones fuse together. Therefore, the correct answer is:
- a) 26 in adulthood
In adults, the vertebral column is typically made up of 26 bones: 24 individual vertebrae and two fused vertebrae that form the sacrum and coccyx. In infants, there are 33 vertebrae (7 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 4 coccygeal), but due to the fusion of some of these bones during growth, the total number decreases in adulthood. So while option b) 33 as an infant is correct for infants, option d) both a and b is misleading as it implies both totals are applicable in adulthood. Thus, the most accurate response reflecting the number of bones in the vertebral column in adulthood remains a) 26.