题目内容：
第三篇 Smart Exercise Doctors are starting to find more and more information that suggests a connection between exercise and brain development. Judy Cameron, a scientist at Oregon Health and Science University, studies brain development. According to her research, it seems that exercise can make blood vessels, including those in the brain, stronger and more fully developed. Dr. Cameron claims this allows people who exercise to concentrate better. As she says: "While we already know that exercise is good for the heart, exercise can literally cause physical changes in the brain."The effects of exercise on brain development can even be seen in babies. Babies
who do activities that require a lot of movement and physical activity show greater brain development than babies who are less physically active. With babies, even a little movement can show big results. Margaret Barnes, a pediatrician (儿科医师)， believes in the importance of exercise. She thinks that many learning disabilities that children have in elementary school or high school can be traced back to a lack of movement as babies. "Babies need movement that stimulates their five senses. They need to establish a connection between motion and memory. In this way, as they get older, children will begin to associate physical activity with higher learning," says Margaret.
Older people can beef up their brains as well. Cornell University studied a group of seniors ranging in age from seventy to seventy-nine. Their study showed a short-term memory increase of up to 40 percent after exercising just three hours a week. The exercise does not have to be very difficult, but it does have to increase the heart rate. Also, just like the motion for infants, exercise for older people should involve some complexity. Learning some new skills or motions helps to open up memory paths in the brain that may not have been used for a long time.
For most people, any type of physical activity that increases the heart rate is helpful. The main goal is to increase the brain's flow of blood. And your brain can benefit from as little as two to three hours of exercise a week.Research by Dr. Cameron seems to suggest that exercise can A．generate new blood vessels,
B．change the way a person think
C．promote brain developmen
D．divert one's attention,
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