If you want to stay young,sit down and have a good think．This is

If you want to stay young,sit down and have a good think．This is the research result of professor Faulkner,who says that most of our brains are not getting enough exercise and as a result,we are ageing unnecessarily soon. Professor Faulkner wanted to find out why healthy farmers in northern Japan appeared to be losing their ability to think and to reason at a relatively early age,and how the process of ageing could be slowed down. He set about measuring brain volumes of a thousand people of different ages and occupations． Computer technology enabled him to obtain precise measurements of the volume of the front and side sections of the brain,which relate to intelligence and emotion,and determine the human character． Contraction of front and side parts--as cells die off--was observed in some subjects in their thirties,but it was still not evident in some sixty-and seventy-year-olds. Faulkner concluded from his tests that there is a simple way to slow the contraction—using the head. The findings show that contraction of the brain begins sooner in people in the country than in the towns．Those least at risk,says Faulkner,are lawyers,followed by university professors and doctors．White--collar workers doing routine work are,however,as likely to have shrinking brains as the farm worker,bus driver and shop assistant. Faulkner's findings show that thinking can prevent the brain from shrinking．Blood must circulate properly in the head to supply the fresh oxygen the brain cells need．"The best way to maintain good blood circulation is through using the brain,"he says．"Think hard and engage in conversation．Don't rely on pocket calculators." Professor Faulkner wanted to find out__．
A、how people's brains shrink
B、the way of making people live longer
C、the size of certain people's brains
D、why certain people aged sooner than others
【正确答案】：D
【题目解析】：根据文章内容，教授Faulkner的研究目标是找出为什么健康的日本北方农民在相对较早的年龄就失去了思考和推理的能力，以及如何减缓衰老的过程。这表明他试图探索的是某些人为何会比其他人更早衰老的原因。 我们逐项看选项： A. 如何人们的大脑萎缩（how people's brains shrink）：虽然文章提到了大脑萎缩的现象，但这并不是Faulkner最初想要研究的问题。 B. 让人活得更久的方法（the way of making people live longer）：文章中并没有直接提及让人活得更久的方法，而是关注大脑衰老的过程。 C. 某些人的大脑大小（the size of certain people's brains）：虽然Faulkner测量了不同年龄段和职业的人的大脑体积，但这只是他研究的一个步骤，不是他的主要研究目标。 D. 为什么某些人比其他人更早衰老（why certain people aged sooner than others）：这与Faulkner的研究目标直接相关，他正是想要找出为什么健康的农民在较早的年龄就失去思考和推理能力的原因。 因此，正确答案是D。