Which of the following vertebra is formed from four vertebrae ?
The cervical and the lumbar vertebrae form an outward curve, which is called (i)_______, while the thoracic and sacral vertebrae form an inward curve called (ii)_______.
The cervical as well as the lumbar vertebrae form an outward curve, which is called ------------, while the thoracic and sacral vertebrae form an inward curve called -------------.