An Australian researcher is urging parents to load up their teenager’s backpack and make t

An Australian researcher is urging parents to load up their teenager’s backpack and make them walk to school.
Professor Leon Straker says students who walk or cycle to school are less likely to have back and neck pain. But the study of 1,202 Western Australian 14­year­old found that 72% of students travelled to school by car or bus. Straker says the study suggests walking or cycling while carrying a schoolbag helps improve trunk (躯干) and spinal (脊柱的) muscle strength.
This helps reduce back pain because greater muscle strength improves support for the back during load carrying .Despite advocating that parents get their children moving，Straker warns bag load should not exceed (超过) 15% of body weight.
Straker says the study also stresses that neck pain is as mon as back pain among young teenagers. This is an area that has been largely ignored，he says，but can be an important indicator of neck pain into adulthood.
For the study，students were asked a series of questions such as how long they carried their bags for，how they carried their schoolbags，the method of travel，and their perceptions(感觉) about the bag’s weight.
Straker says about half of all participants experienced back and neck pain，with slightly more females reporting neck pain. However，the gender (性别) difference may also be due to the fact that females have lower pain tolerance.
Studies from the 1980s found carrying a bag over one shoulder was most mon among teenagers. However in this study 85% of participants carried their bag over both shoulders.
Straker believes the change has been driven partly through education campaigns，but also by increasing fashion status of backpacks and improved design.
【小题1】In the opinion of Leon Straker，parents should    .A．reduce the load of their children’s schoolbagsB．put more books in their children’s schoolbagsC．get their children’s schoolbags ready for schoolD．ask their children to walk to school carrying schoolbags【小题2】If a child weighs 40 kilograms，the weight of his schoolbag should be    .A．no more than 15 kgB．less than 6 kgC．as heavy as 9 kgD．more than 6 kg【小题3】We can learn from the passage that    .A．most of the students in Australia walk to schoolB．neck pain is unmon among young teenagersC．walking while carrying a backpack helps reduce back painD．males are more likely to experience back pain than females【小题4】According to the passage，what change has taken place since the 1980s?A．How students carry their schoolbags.B．How heavy students’ schoolbags are.C．How students go to school every day.D．How long students carry their schoolbags for.D