Which of the Following Is a Valid Hypothesis,considering Both the Hebbian

Which of the following is a valid hypothesis,considering both the Hebbian Learning Rule and evidence that there is a decline in the number of synapses in the human brain after about age 1

A)  Because we use only 10 percent of our brain at any given time, the decline in synapses after age 1 has no impact on functioning. 
B)  We create new connections in infancy, and unless all the necessary connections are made before we are a year old, we will have difficulty learning for the rest of our lives because we start losing brain cells so early. 
C)  Although the number of synapses decreases throughout the life span, the number of neurons does not decrease, and having a large number of neurons is more important than having a large number of synapses. 
D)  Although creating new connections between neurons is important, it is also important to get rid of unnecessary or outdated connections in order to enhance the efficiency of processing within our brains.