What embryonic structure gives rise to the centrum?

The sclerotome that gives rise to the centrum.

Explanation:

During embryological development the embryonic structure that gives to centrum is the sclerotome arise from the paraxial mesoderm. Cells of the sclerotome move to surround the spinal cord and notochord medially to form the mesenchymal column.  

The cells of the sclerotome move in 3 directions :

-The caudal part and the cranial part of sclerotome forms densely packed cells and loosely packed cells respectively.

-Some of the thickly packed cells move opposite the center myotome and give rise to the intervertebral disk .

-The rest cells fuse with the remaining cells of the sclerotome to form the mesenchymal centrum of the vertebra.

c) 50% there are four chromosomes. after crossing over, 2 of the four have been changed. that means any gamete has a 2 in 4 chance or 50% chance of receiving the mutated chromosome.

i think it is d. objects resist changes in their state of motion.