[originaltext]At the start of each school year, millions of parents buy their c

At the start of each school year, millions of parents buy their children new backpacks. Many are constantly worried that not choosing the right bag could leave their kids with long-term back or spinal pain. But Dr. Michael Holmes, of Brock University in Ontario, Canada, says there is no evidence that backpacks can cause back pain or damage to the spine. In fact, he says, not going for a backpack—and opting for a shoulder bag— could be what causes the real harm.
Some studies have found an association between how a child carries a backpack and changes in head and neck posture. However, a review published in the British Journal of Sports Medicine back in May looked at five longitudinal studies and 63 cross-sectional studies on this subject. The authors found that most of the evidence of the link between backpacks and back pain came from cross-sectional studies, which only measured the pain at a single point. But the evidence is not considered as strong as longitudinal studies, which follow participants over a period of time.
Dr. Holmes says purchasing a good pack is only half the battle. It needs to be worn properly. He says parents should teach children to wear backpacks with both shoulder straps, encourage them to store what they don’t need in their lockers and desks, and to be active to help prevent injuries.
Questions 22 to 25 are based on the passage you have just heard.
22. What are many parents worried about at the start of each school year?   
23. What does Dr. Michael Holmes say?   
24. What does the review published in May find about the link between backpacks and back pain?   
25. What should parents do according to Dr. Holmes?