A. The waste of lithium in the world．

B. The increasing number of electronic devices．

C. The development of technology．

D. The pollution caused by batteries．

1. It can be learned from the passage that ______ ．

A. energy-harvesting products save money in the long run

B. taller people can surely produce a larger amount of power

C. automatic watches harvest energy from the users'body heat

D. two ways of harvesting energy are mentioned in the passage

2. Which of the following might be the best title for the passage？ ______

A. Energy harvesting：a low-risk technology

B. Energy harvesting：a high-profit technology

C. Energy harvesting：a problem-free technology

D. Energy harvesting：an environment-friendly technology．

You know the saying"You're as young as you feel．"Well，there may be some truth to that，according to researchers at Harvard and the Massachusetts Institute of Technology．

Ellen Langer，a Harvard psychologist who studies how the mind influences the body，and colleagues reviewed the scientific literature for evidence that a person's perception of their age might influence their health．They published their results in the journal Perspectives on Psychological Science．

In one study that Langer led，47 women had their hair done．The women who thought their new hairdos made them look younger did look younger to objective observers，who were shown before-and-after pictures．The women who thought they looked younger also showed a drop in blood pressure．Another study involving 4，421 men found that those who became bald （秃顶）at a relatively young age were more likely to get cancer and heart disease than men who did not．Similarly，another study involving 2，017 men found that those who lost their hair early were more likely to develop heartdisease．"We believe that the feelings associated with being older than one's real age account for some of these health outcomes，"the researchers wrote．

The researchers also described studies that found that women who had children later in life were more likely to be healthier and live longer than those who had children early，which they attributed to the fact that these mothers tend to spend more time with younger women．Similarly，people who marry younger partners tend to live longer than those who marry older partners，according to other studies．

Taken together，the research"supports the general mind-body hypothesis （假说）that when a younger mind is prepared，a younger body can accompanyit．"While the mechanism （机制）remains unclear，the researchers figured that suggestions associated with aging can"make one unconsciously or consciously aware of old age and set in