[单选题]下列试剂不需要保存在棕色瓶中的是（??）
A氯水
B氨水
C硝酸
D硝酸银
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1.Strange thing happens to time when you travel. Because the earth is divided into twenty-four time zones one hour apart, you can have days with more or fewer than twenty-four hours, and weeks with more or fewer than seven days.If you make a five-day trip across the Atlantic Ocean, your ship enters a different time zone every day. As you enter each zone, the time changes the hour. Travelling west, you set your clock back; travelling east, you set it ahead. Each day of your trip has either twenty-five or twenty-three hours.If you travel by ship across the Pacific you cross the international date line. By agreement, this is the point where a new day begins. When you cross the line, you change your calendar the full day, backward or forward. Travelling east, today becomes yesterday; travelling west, it is tomorrow!(5分)1.1The best title for this selection is____.(1分)A. Trip Across the AtlanticB. How Time Changes Around the World C. Crossing the International Date LineD. How Time Zones Were Set Up
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34、摄影诞生时期存在着的两种摄影方法是( )
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3. Friction is a force which opposes motion. Much of the energy supplied to a complicated machine with many moving parts is wasted in overcoming this opposition. The energy is converted into useless heat. The amount thus lost can be considerably reduced and the life of the machine prolonged by careful lubrication. This reduction improves the efficiency of the machine. Another way in which friction is reduced is to substitute roller or ball bearings for the earlier type of bearing, in which the surfaces in contact move by sliding. Bearings of these later types are used very extensively in many kinds of modern machinery.It must not be assumed, however, that friction is always a disadvantage. In many instances it is highly important. Belts are often used in conveying power from one machine to another. In the absence of friction, this could not be done. The driving wheel would not run the belt, neither would the belt run the wheel to driver. Without friction, then, belted machinery could not be used. Again in the case of all motor vehicles, friction is essential in the operation of the brake. Were there no friction, there could be no brake. But even this illustration does not give an adequate picture of the importance of friction. The vehicle could not even be started if it were not for the friction exerted between the tires and the road. Nails hold in wood, and screws hold in either wood or metal by reason of friction, without which they would be useless. Walking is difficult enough on an icy pavement, but it would be wholly impossible if there were no friction at all between the shoe and the pavement.(5分)3.1 Friction arises when____.(1分)A. an opposing force of motion exists B. the energy is wastedC. everything is motionlessD. a complicated machine is supplied with energy
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下列哪些选项属于货币政策委员会的职责（）.
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22. T.S.Eliots most popular verse play is ______.
