题目

Nine out of 10 people have run up unsecured debt and many fear they will never be able to pay back what they owe, a survey has claimed.        Around 89% of people aged between l|8 and 35 said they owed money on a credit card, loan or overdraft, the research showed．        A third of people admitted they did not think- they would ever be debt-free, 54% of whom said they would always need to borrow money in order to fund the lifestyle they wanted．        One in five of these people also claimed they were not worried about the possibility of their debts being passed on to t如图所示为一列简谐波在时刻的图象，已知质点M的振动方程为（cm），此波中质点M在____________s时恰好第3次到达y轴正方向最大位移处，该波的波速为____________m/s。