频率的单位是______，简称赫，符号______．
题型：填空题
问题：
频率的单位是______，简称赫，符号______．
题型：填空题
You maybe surprised to learn that one of the best steps you can take to protect your health is to step outside and spend some time in the grass, dirt and water．
Our ancestor
s enjoyed the healing power of nature , and now scientists are starting to catch up．According to research in recent years, just having a view of nature has been shown to improve hospital patients' recovery and reduce illness rates among office workers．Also, exposure （曝露）to wildlife, horseback riding, hiking, camping and farms can be helpful for a variety of health conditions in adults and children．
Much of this type of research is focusing on children, and in fact an entire movement has quickly developed to connect kids with the healing power of nature．
Obesity （肥胖）．Rates of childhood obesity have grown sharply in recent years, and this is partly because of reduced outdoor activity time．Increasing the time students spend learning about nature, both in and outside the classroom, would help solve this problem．Such lessons are often more attractive for students and often lead them to become more active outside．
Attention deficit hyperactivity disorder （ADHD） （注意力缺失症）．Exposure to ordinary natural settings （环境） in the course of common after-school and weekend activities may be effective in reducing attention deficit symptoms in children．Participation in green activities —such as nature walks—helped ADHD patients from a wide range of backgrounds to stay focused and complete tasks．
Stress．Access to nature, even houseplants, can help children cope with stress．
Depression and seasonal emotional disorder．Major depression requires medical treatment, but physical activity, especially outdoors, can help ease symptoms．For your average case of winter blues, experts suggest spending time outside every day and, if possible, taking the family to a sunny vacation spot in mid-winter．
Experts emphasize that you needn' t go to wilderness preserves to enjoy nature' s benefits—simply walking in a city park or growing in a rooftop garden can make a difference．
小题1:It can be inferred from the first two paragraphs that____．
A．ancient people were not familiar with the healing power of nature．
B．modern people are not familiar with the healing power of nature．
C．the healing power of nature works better on children．
D．the healing power of nature works better on office workers．小题2:According to Para．4, lessons about nature_____．
A．should engage parents in them
B．should take place outdoors
C．are used widely at schools
D．are liked by students小题3:Exposure to green areas in neighborhoods can_____．
A．improve children' s skills at learning
B．help reduce ADHD symptoms
C．treat major depression
D．cure winter blues小题4:What can be inferred from the last paragraph?
A．You can only enjoy nature's benefits in the wilderness．
B．A common natural setting is beneficial to your health．
C．A city park and a rooftop garden have different benefits．
D．Too many people in the wilderness will reduce the benefits of nature．