I found the possible choices on the internet.
"-incapability of the brain to develop simultaneously in multiple areas.-differences in the timing of development of different skills and behavioral categories.-different rates of synapse elimination.-All of the answers are correct."
All of the answers are correct.
Synapse production usually may have different rates through out the human development but when there different rates in different areas of the brain at the same point in time, it can indicate that those areas are not all equally developed, there are different times for different skills and behavioural categories, or there are slower or faster rates of synapse elimination which is the process of eliminate redundant or useless synapse connections, strengthening well established circuits.