Many developmentalists are concerned that modern children spend too little time

i would say b. research typically uses a variety of sources

is there multiple choice or do you need like an essay answer?

answer; humanistic;

i believe the answer is: true

our brain need to reach a certain level of development   before it could interpret and understood sound with high difficulties. to proof this, we just need to pay attention in musical preference between children and adults. it is far less likely that children would enjoy things such as orchestra or rock band as much as adults due to the difference in this ability.