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请认真阅读下面短文,从短文后各题所给的A、B、C、D四个选项中,选出最佳选项。

C

    Do you have brown hair? Are you taller than other kids your age? These characteristics were decided before you were born. You got your traits from your parents. They passed their traits on to you through genes (基因).

    Genes carry codes (代码) for blue eyes or brown eyes. Genes say how tall you will get and what color hair you will have. You got half of your genes from your mother. You got half of your genes from your father. So you have your own set of genes. Each person gets different genes for each body part. That is why you look like but not exactly like your brother or sister.

    A dominant (显性的)  gene shows up most of the time. Brown eyes are dominant over bluc eyes. A recessive (降性的)  gene shows up less often. Light hair comes from a recessive gene. Dark hair is more common. Look at the eye color and hair color of the people around you. You will see that this is true.

    Genes help to make you who you are. But they don't tell the whole story. Your genes may help you to be fast and strong. But you still need to learn how to run or swim or skate well.

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    Optimism May Help People Live Longer

People who have an optimistic view on life are more likely to live longer, a US study said Wednesday.

    The study, published in the American Journal of Epidemiology, analyzed data from 2004 to 2012 from 70,000 women enrolled in the Nurses' Health Study, a long-running US study tracking women's health via surveys every two years.

    The researchers looked at participants' levels of optimism and other factors that might play a role in how optimism may affect mortality risk, such as race, high blood pressure, diet, and physical activity.

    It found the most optimistic women, or the top 25%, had a nearly 30 percent lower risk of dying from any of the diseases analyzed in the study compared with the least optimistic women, or the bottom 25%.

    The most optimistic women had a 16 percent lower risk of dying from cancer; 38 percent lower risk of dying from heart disease; 39 percent lower risk of dying from stroke; 38 percent lower risk of dying from respiratory disease; and 52 percent lower risk of dying from infection.

    Previous studies have linked optimism with reduced risk of early death from cardiovascular (心脑血管的) problems, but this was the first to find a link between optimism and reduced risk from other major causes.

    “While most medical and public health efforts today focus on reducing risk factors for diseases, evidence has been mounting that enhancing psychological resilience (弹性,复原力) may also make a difference,” said Eric Kim, research fellow at the Harvard T.H. Chan School of Public Health and co-lead author of the study.

    “Our new findings suggest that we should make efforts to boost optimism, which has been shown to be associated with healthier behaviors and healthier ways of coping with life challenges.”

    The study also found that healthy behaviors only partially explain the link between optimism and reduced mortality risk. One other possibility is that higher optimism directly affects our biological systems, Kim said.

    Co-lead author and postdoctoral research fellow Kaitlin Hagan said optimism can be varied with relatively uncomplicated and low-cost interventions (干预), even things as simple as having people write down and think about the best possible outcomes for various areas of their lives, such as careers or friendships.

    “Encouraging use of these interventions could be an innovative way to enhance health in the future,” Hagan said.