问题详情

Man"s forehead will grow larger because______.
A．he will make use of only about 20% of the brain"s capacity
B．the other 80 ~Jo of his brain will grow in due time
C．he had rather narrow forehead a few hundred years ago
D．he will have to use his brain more and more as time goes on请帮忙给出正确答案和分析，谢谢！