题目

如图所示,公园蹦极跳床深受儿童喜爱.一小孩系好安全带后静止时脚刚好接触蹦床,将小孩举高至每根轻质弹性绳都处于原长时由静止释放,对小孩下落过程的分析,下列说法正确的是（） A . 小孩一直处于失重状态 B . .弹性绳对小孩的作用力一直增大 C . 小孩的加速度一直增大 D . 小孩的机械能一直减小Most Americans who earned money last year are expected to pay the I．R．S． part of what they earned． Only those who earned very little are not required to make such a payment．They still must send a tax report to the government． Most American workers have already paid all or most of their federal income taxes．This is because part of the tax goes to the I．R．S．each time a worker is paid．The government returns some of the money if too much was withheld． People who work for themselves usually send a tax payment to the I．R．S．every three months． The federal tax rate is not the same for everyone．People who earn a lot of money pay taxes at a higher rate than those who earn less．But even people who earn the same amount do not always pay the same amount of tax．That is because of the many tax laws written by Congress．These laws were created for social or economic purposes． For example, people who borrow money to buy a house may pay less in taxes than people who rent a home． Homeowners can subtract （减掉） the interest on the loan from their taxable income．Americans also can help reduce their taxable income by subtracting the value of money given to organizations that help the needy． Personal income tax is not the only tax that the federal government collects．It taxes property or money left when someone dies．And it taxes earnings from the sale of some investments, such as a house．Americans also pay a federal social security tax that is used to pay retired workers． Americans pay many other taxes, too．Most pay taxes to the state in which they live．Most states also collect sales tax．That is an amount added to the cost of goods bought in stores． And local city and county governments collect tax on property its citizens own．Many Americans say they pay too many taxes and their taxes are too high．Others say they are willing to pay taxes to receive services from their local state and federal governments． 1．Why are some people willing to pay taxes? Because ____． A． they want to receive services from their local state and federal governments B．they wanted to make contributions to their country C．part of the money goes to the I．R．S． D．the tax laws were created for social or economic purposes 2．Why don’t the people who earn the same amount of money always pay the same amount of tax? Because ____． A．some people are rich and others are poor               B．they live in different areas C．they pay the taxes according to different tax laws D．some people don’t want to pay too much money 3．Who might pay sales tax? ____． A．Stores          B．Consumers          C．Salesmen               D．Factories 4．Which of the following is wrong? ____． A．The persons who earn very little may not pay personal income tax B．People who borrow money to buy a house may pay less in taxes than people who rent a house C．The money left by a dead person can be taxed D．The federal tax rate is the same for everyone