按照发声机理的噪声源可分为哪三类，并对这三类噪声进行解释？

如图所示，挡板P固定在足够高的水平桌面上，质量分别为m_A和m_B的小物块A、B大小可忽略不计，分别带有+Q_A和+Q_B的电荷量，两物块由劲度系数为k的绝缘的轻弹簧相连，一不可伸长的轻绳跨过滑轮，一端与B连接，另一端连接一轻质小钩，整个装置处于场强为E、方向水平向左的匀强电场中。A、B开始时静止，不计一切摩擦及A、B间的库仑力，A、B所带电荷量保持不变，B不会碰到滑轮。

（1）若在小钩上挂一质量为M的物块C由静止释放，可使物块A恰好能离开挡板P，求物块C下落的最大距离。

（2）若C的质量改为2M，则当A刚离开挡板P时，B的速度多大。

下列关于水泥的说法，正确的有（）

A.水泥是由水泥熟料、石膏和混合料磨细而成的一种水硬胶凝材料

B.水泥颗粒粒径愈细，水化愈快，则其早期强度高，而后期强度较低

C.初凝时间不符合规定的水泥属于废品

D.水化热对大体积混凝土工程是有益的

E.在干燥环境中应优先选用粉煤灰水泥

There have been many great inventions, which have changed the way we live. The first great invention was one that is still very important today---the wheel. This made it easier to carry heavy things to travel long distances. For hundreds of years after that there were few inventions that have made as much effect as the wheel. There was little unknown land left in the world. People didn't have to explore(开发) much any more. They began to work instead to make life better.

In the second half of the 19th century many great inventions were made. Among them were the camera, the electric light and the radio. These all became a big part of our life today. The first part of the 20th century saw more great inventions. The helicopter in 1909. Sound movies in 1926. The computer in 1928, and jet planes in 1930. This was also a time when a new material was made. Nylon came out in 1935. It changed the kind of clothes people wear. The middle part of the 20th brought new ways to help people get over diseases. They worked very well. They made people healthier and let them live long lives. By the 1960s most people could expect to live to be at least 60. By this time most people had a very good life. Of course new inventions continued to be made. But man now had a wish to explore again. The world is known to man but the stars are not yet. Man began looking for ways to go into space. Russia made the first step. Then the United States took a step. Since then other countries, including China and Japan, have made their steps into space.

68. The first great invention ever known was ______.

A. the camera               B. the wheel                 C. the electric light        D. the radio

69. Which of the following was turned out nearly at the same time with the jet plane?

A. The radio.                                                   B. The camera.             

C. Nylon.                                                               D. The helicopter.

70. This passage talks mainly about ______.

A. how inventions affect (影响) people's life      B. when electric light was invented

C. which country made the first step into space    D. why cars were very important

71. We can safely come to the conclusion that people's life will be made even better through ______.

A. new discoveries                                         B. greater inventions

C. better ways to help people get over diseases  D. all of above

左中上腹持续剧痛，并阵发性加剧多见于（）

A.急性弥漫性腹膜炎

B.胆道蛔虫症

C.十二指肠溃疡

D.急性胰腺炎

E.胃溃疡

阅读材料，回答相关问题：

16至17世纪的中国，新的经济形态还十分微弱、脆嫩，明清时期的早期启蒙思想家们先天不足，具有一种时代性的缺陷。……黄宗羲、唐甄们提不出新的社会方案，而只能用扩大相权、限制君权、提倡学校议政等办法来修补封建专制制度。

孟德斯鸠、卢梭们则拿出了“三权分立”、君主立宪制、民主共和制这样的资产阶级国家蓝图。这表明，中国明清时期的进步思想与18世纪欧洲启蒙思想属于两个不同的历史范畴。前者是中世纪末期的产物，后者是近代社会的宣言书。

——张岱年、方克立主编《中国文化概论》

请回答：

17世纪中国的启蒙思想只能称作“中世纪末的产物”而18世纪法国的启蒙思想却成为“近代社会的宣言书”根据材料并结合所学知识分析造成东西两种不同状况的根本原因是什么？