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金融期权是一种所有权，是持有者决定是否买卖某种金融商品的所有权。()
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证券交易的特征主要表现为证券的流动性、收益性和风险性。()
某投资者在上海证券交易所以每股15元的价格买入XX（A股）股票20 000股，那么，该投资者最低需要以()元全部卖出该股票才能保本（佣金按2‰计收，印花税、过户费按规定计收，不收委托手续费）。
B股实行()起回转交易。()
Pushbike Peril
Low speed bicycle crashes can badly injure or even kill children if they fall onto the ends of the handlebars(车把) so a team of engineers is redesigning the humble handlebar in a bid to make it safer.
Kristy Arbogast, a bioengineer at the Children's Hospital of Philadelphia in Pennsylvania, began the project with her colleagues after a study of serious abdominal(腹部的) injuries in children in the past 30 years showed that more than a third were caused by bicycle accidents. "The task was to identify how the injuries occurred and come up with some countermeasures(对策)." she says.
By interviewing the children and their parents, Arbogast and her team were able to reconstruct(重建；重构) many of the accidents and identified a common mechanism responsible for serious injures. They discovered that most occur when children hit an obstacle at a slow speed, causing them to topple over. To maintain their balance they turn the handlebars through 90 degrees, but their momentum (冲力) forces them into the end of the handlebars. The bike then falls over and the other end of the handlebars hits the ground, ramming it into their abdomen.
The solution the group came up with is a handgrip(握柄) fitted with a spring and damping(制动的；减速的，缓冲的) system. The spring absorbs up to 50 per cent of the forces transmitted through the handlebars in an impact. The group hopes to commercialize(使商品化) the device, which should add only a few dollars to the cost of a bike. "But our task has been one of education because up until now, bicycle manufacturer were unaware of the problem. " says Arbogast.
The team has also approached the US Consumer Product Safety Commission to try to persuade manufacturers to adopt the new design. A decision is expected later this year.
According to the passage, some engineers are trying to improve the handlebars because
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