The options are missing from the question.
Below are the options.
a. To help stabilize the trunk over the upper spine, and to prevent dorsal slipping of the cervical vertebrae.
b. To prevent the creation of an s-curved spine, typical of quadrupedal organisms.
c. To facilitate the bicondylar angle of the foramen magnum.
d. To help stabilize the trunk over the lower spine, and to prevent ventral slipping of the lumbar vertebrae.
The correct answer to the question is option D.
TO HELP STABILIZE THE TRUNK OVER THE LOWER SPINE,AND TO PREVENT VENTRAL SLIPPING OF THE LUMBER VERTEBRAE
The wedge shape of the lumber vertebrae and it's coronal orientation helps in facilitating bipedal locomotion and bearing of load. It is also reduces the efforts of the muscles as it walks in bipedal locomotion.
It has a way of helping to decrease the negative effects forc has over the vertebrae and the spinal cord.
Finally, It also helps by bringing the center of gravity to the feet.