The professor's tests show that __. A．our brains shrink as we grow old B．the front section of the brain does not shrink C．seventy-year-olds have better brains than sixty-year-olds D．brain contraction may vary among people of the same age
A.our B.the C.seventy-year-olds D.brain
【参考答案】
D 从第五、六、七段可知，通过对30岁的人测试(60、70岁不是很明显)，教授发现减轻大脑萎缩的最简单的方法是：......