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问题 单项选择题

Hagenuk电/液伺服器中各元件的作用是（）。

①先导阀的作用使伺服器具有超前控制；

②先导阀的作用是引导主阀使其跟随动作；

③平衡泵的作用是促使先导阀平衡；

④滑阀及其活塞的作用是保证动力油压恒定；

⑤反馈弹簧的作用是将动力活塞的位移转换成反馈作用力；

⑥旁通阀的作用是沟通动力活塞上下空间之油压。

A.①②④⑥

B.①③④⑤

C.②③⑤⑥

D.②④⑤⑥

答案

参考答案：D

单项选择题

1 Millions of teens are on weight-reducing diets. Although maintaining a healthy body weight is important, obsessive dieting can lead to eating disorders. Eating disorders can disrupt lives and sometimes even result in death.
Starving Oneself
2 Anorexia nervosa is an eating disorder in which people starve themselves. Anorexics have an irrational fear of becoming fat and see themselves as much heavier than they really are. They shun food and may exercise for hours every day in an attempt to lose weight.
3 Female anorexics may never mature sexually or may stop menstruating because they lose too much body fat, causing the level of sex hormones to fall. Their body temperature and pulse rate become abnormally low; their hair becomes thin and dry; and their resistance to infection drops.
Bingeing and Purging
4 Patients with bulimia engage in frequent episodes of bingeing (eating a large amount of food in a short time). After a binge, they almost always purge by self-induced vomiting or by using laxatives. Therefore, their weight stays fairly constant. Unlike anorexic patients, bulimics often recognize that their behavior is abnormal and often feel guilty, depressed, and helpless.
5 The frequent purging removes salts from the body, which can eventually lead to muscle weakness, heart failure, and kidney disease. The vomiting gradually destroys tooth enamel and results in unhealthy gums.
Help for People with Eating Disorders
6 Little is known about what causes anorexia nervosa and bulimia. Many people believe that western society’s emphasis on thinness in women is largely to blame. However, recent research suggests that genetic factors might also be involved. Both eating disorders can be managed with a combination of medical treatment, counseling, and family support.

What may be the influence of anorexia on female

A．muscle weakness and heart failure

B．kidney disease and low body temperature and pulse rate

C．dropping resistance to infection

D．destroyed tooth enamel and unhealthy gums
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选择题

—Nancy,  you are late today!

—Sorry, I ______ next time, Miss Li. [ ]

A. don't

B. won't

C. am not

D. haven't

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