In 2015，researchers from Australia's Deakin University published one of the first studies measuring food's physical effect on the left hippocampus（海馬體），a seahorse-shaped brain region crucial for memory，learning，and decision making.It is also one of the first areas to shrink in people with Alzheimer's disease and other forms of dementia （癡呆）.255 people filled out diet surveys and then underwent MRI scans（磁共振掃描成像） that measured their brains.Four years later，they returned for another scan in response to a request from the researchers.
   The study found that the left hippocampus was bigger and heavier in the healthy eaters than in the unhealthy ones，regardless of age，sex，weight，exercise habits，or general health.That means eating the right foods and skipping the wrong stuff could help protect against declines in thinking and memory that lead to dementia.Healthy eating doesn't just prevent brain decline.It raises scores on thinking and memory tests，according to a study published in March 2019 that tracked 2，621 American women and men for 30 years."Green leafy vegetables have good effects that may protect both females and males against cognitive（認知的）decline and dementia，" says lead researcher Claire McEvoy，RD，of the Centre for Public Health at Queen's University Belfast in Northern Ireland.
   Even a little healthy food goes a long way.According to a 2018 Rush University study that tracked 960 people for 4.7 years participants who ate just 1.3 extra servings of green leafy vegetables a day showed cognitive abilities similar to those of people 11 years younger.
   How are these power foods working with your brain cells？Animal and test-tube experiments suggest that compounds in healthy diets help new cells make copies of DNA when they divide and multiply.Meanwhile，high-fat，high-sugar processed foods harm brain cells.
   While food serves as an important brain protector，experts say brain supplements（補品）aren't all that effective.Studies show that they don't make brain cells active in a significantly positive way."Let the buyer be cautious，" says David Hogan，MD，a specialist at the University of Calgary.A study of nootropics（益智藥） in the November 2019 Journal of the American Medical Association revealed that the unapproved drug-piracetam（乙酰胺吡咯烷酮） was found in four out of five brands tested，at levels that could cause side effects such as depression.

（1）Why did the researchers have the 255 people return for another MRI scan four years later？

B

B

A．To test whether they had Alzheimer's disease.
B．To see what effects diets had on the left hippocampus.
C．To study how they kept healthy in the four years.
D．To deepen their research into Alzheimer's disease.
（2）What can we infer from Paragraph 2？

A

A

A．Healthy eating helps to reduce the risk of dementia.
B．Unhealthy diet is a major contributing factor in cognitive decline.
C．Age and sex have nothing to do with our general health.
D．Plant-based diets have greater effects on women than men.
（3）Which of the following would David Hogan most probably agree with？

C

C

A．Brain supplements are as helpful as healthy diets.
B．We'd better take brain supplements for convenience.
C．We should be careful when taking brain supplements.
D．Brain supplements have as many side effects as processed foods.
（4）What might be the best title for the passage？

A

A

A．Yes to Green Leafy Vegetables
B．Yes to Nootropics
C．No to Intelligence
D．No to Dementia