问题详情

At the end of the passage, Kevin Mitchell implies that______.

A．the biological system is very delicate and its balance is easily broken

B．after a long and hard process, human genes come to what they are today

C．genetic mutations in the human body are developed in a casual manner

D．some people may have a higher risk of brain cancer than others

请帮忙给出正确答案和分析，谢谢！