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A．To talk with Mary about going to the concert.B．To ask Mary to stop worrying about th
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In the design considerations of a spaceship, fuel choice is as important as the method of
听力原文： We know that we have to pay for what we get. If we buy food, We know there will be a bill to pay. These are private bills. But there are also public bills that must be paid. Public bills are paid by the government. In turn we get these services through taxes. What would happen if everyone in the city stopped paying taxes？ The water supply would stop; water might become unclean and impure. The streets might not be cleaned. There would be no police force to protect people and property. Schools would be closed. People would become sick and diseases might spread. We should not want to live in such a city. We all want pure water and food, clean streets and good schools. We want the police to prevent crime. The chief duty for every government is to protect persons and property. More than three quarters of the money spent by our government is used for this purpose. The next largest amount of public money goes to teach and train our citizens. Billions of dollars each year are spent on schools and libraries. Public money is used to pay the teachers and all the public officials. A large number of public funds are also spent on roads.
The greatest part of necessary funds is raised by taxes. A tax is money that we all must pay to support the government. The law orders us to pay taxes. We have no choice in the matter. Almost everyone pays some taxes in one form. or another.
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如图所示多跨桥，由L=20m简支梁组成，采用支撑于岩基上的柔性墩。墩的几何尺寸见图。桥墩混凝土采用C25，混凝土线膨胀系数为1×10°/℃。除0号墩及5号墩上分别设置滚动支座外，其他桥墩上均为固定支座(五跨一连)。
当桥梁结构温度均匀变化时，梁体无水平位移的“零点位置”离2号墩的距离口最接近的数值是______。
放松钢筋时，截面上下边缘的混凝土预应力与______项数值最为接近。(提示：计算时仅考虑第一批预应力损失，此时预应力钢筋的合力NpoI=684.31kN，预应力钢筋合力作用点至换算截面重心轴的偏心距epoI=299.6mm)
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