区段无煤柱护巷有（）和（）两种方法，沿空留巷一般适用于开采缓斜和倾斜、厚度在2m以下

确定国家基本药物制度框架的机构是（）

A.卫生行政部门

B.国家药品监督管理部门

C.人力资源和社会保障部门

D.国家基本药物工作委员会

钢铁是人类生活和生产中重要的材料．下列关于钢铁的说法错误的是（　　）

A．生铁和钢是含碳量不同的铁的两种合金

B．工业上冶炼钢铁的原理是：用一氧化碳在高温条件下把铁从铁矿石里还原出来

C．铝合金比铁制品耐腐蚀的原因是铁的化学性质比铝活泼

D．铁生锈的过程实际是铁与空气中的氧气、水蒸气等发生化学反应的过程

如图所示，光滑水平轨道与半径为R的光滑竖直半圆轨道在B点平滑连接．在过圆心O的水平界面MN的下方分布有水平向右的匀强电场．现有一质量为m，电量为+q的小球从水平轨道上A、点由静止释放，小球运动到C点离开圆轨道后，经界面MN上的P点进入电场（P点恰好在A点的正上方，如图．小球可视为质点，小球运动到C点之前电量保持不变，经过C点后电量立即变为零）．已知A、B间距离为2R，重力加速度为g．在上述运动过程中，求：

（1）电场强度E的大小；

（2）小球在圆轨道上运动时的最大速率：

虽然刘某没有身份证件，由于其租金较高，王某将房屋出租给刘某居住。王某构成将房屋出租给无身份证件人居住的违反治安管理行为。

In 1959 the average American family paid $ 989 for a year’s supply of food. In 1972 the family paid $1,311．That was a price increase of nearly one-third. Every family has had this sort of experience. Everyone agrees that the cost of feeding a family has risen sharply. 41．______.

Many blame the farmers who produce the vegetables, fruit, meat, eggs, and cheese that stores offer for sale. According to the U. S. Department of Agriculture, the farmer’s share of the $1,311 spent by the family in 1972 was $ 521．This was 31 per cent more than the farmer had received in 1959.

But farmers claim that this increase was very small compared to the increase in their cost of living. 42．______These include truck drivers, meat packers, manufacturers of packages and other food containers, and the owners of stores where food is sold. They are among the "middlemen" who stand between the farmer and the people who buy and eat the food. Are middlemen the ones to blame for rising food prices

Of the $1,311 family food bill in 1972, middlement received $ 790, which was 33 percent more than they had received in 1959．It appears that the middlemen’s profit has increased more than farmer’s. 43．According to economists at the First National City Bank, the profit for meat packers and food stores amounted to less than one percent. During the same period all other manufacturers were making a profit of more than five percent. By comparison with other members of the economic system both farmers and middlemen have profited surprisingly little from the rise in food prices.

44．______The economists at First National City Bank have an answer to give housewives, but many people will not like it. These economists blame the housewife herself for the jump in food prices. They say that food costs more now because women don’t want to spend much time in the kitchen. Women prefer to buy food which has already been prepared before it reaches the market.

Vegetables and chicken cost more when they have been cut into pieces by someone other than the one who buys it. A family should expect to pay more when several "TV dinners" are taken home from the store. These are fully cooked meals, consisting of meat, vegetables, and sometimes dessert, all arranged on a metal dish. The dish is put into the oven and heated while the housewife is doing something else. Such a convenience costs money. 45.

Economists remind us that many modem housewives have jobs outside the home. They earn money that helps to pay the family food bills. The housewife naturally has less time and energy for cooking after a day’s work. She wants to buy many kinds of food that can be put on her family’s table easily and quickly. "If the housewife wants all of these, " the economists say, "that is her privilege, but she must be prepared to pay for the services of those who make her work easier. "

It appears that the answer to the question of rising prices is not a simple one. Producers, consumers, and middlemen all share the responsibility for the sharp rise in food costs.

[A] However, some economists believe that controls can have negative effects over a long period of time. In cities with rent control, the city government sets the maximum rent that a landlord can charge for an apartment.

[B] Farmers tend to blame others for the sharp rise in food prices. They particularly blame those who process the farm products after the products leave the farm.

[C] Thus, as economists point out: "Some of the basic reasons for widening food price spreads are easily traceable to the increasing use of convenience foods, which transfer much of the time and work of meal preparation from the kitchen to the food processor’s plant. "

[D] But some economists claim that the middleman’s actual profit was very low.

[E] Who then is actually responsible for the size of the bill a housewife must pay before she carries the food home from the store’

[F] But there is less agreement when reasons for the rise are being discussed. Who is really responsible

[G] Economists do not. agree on some of the predictions. They also do not agree on the value of different decisions. Some economists support a particular decision while others criticize it.

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