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什么叫逐行倒相？PAL制如何克服由相位失真引起的色调失真？
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Moderate Earthquake Strikes England A moderate earthquake struck parts of southeast England on 28 April 2007, toppling chimneys from houses and rousing residents from their beds. Several thousand people were left without power in Kent County. One woman suffered minor head and neck injuries. "It felt as if the whole house was being slid across like a fun-fair ride," said the woman. The British Geological Survey said the 4. 3-magnitude quake struck at 8:19 a.m. and was centered under the English Channel, about 8.5 miles south of Dover and near the entrance to the Channel Tunnel. Witnesses said cracks appeared in walls and chimneys collapsed across the county. Residents said the tremor had lasted for about 10 to 15 seconds. "I was lying in bed and it felt as if someone had just got up from bed next to me." said Hendrick van Eck, 27, of Canterbury about 60 miles southeast of London. "I then heard the sound of cracking, and it was getting heavier and heavier. It felt as if someone was at the end of my bed hopping up and down." There are thousands of moderate quakes on this scale around the world each year, but they are rare in Britain. The April 28 quake was the strongest in Britain since 2002 when a 4.8-magnitude quake struck the central England city of Birmingham. The country's strongest earthquake took place in the North Sea in 1931, measuring 6.1 on the Richter scale. British Geological Survey scientist Roger Musson said the quake took place on 28 April in an area that had seen several of the biggest earthquakes ever to strike Britain, including one in 1580 that caused damage in London and was felt in France. Musson predicted that it was only a matter of time before another earthquake struck this part of England. However, people should not be scared too much by this prediction, Musson said, as the modern earthquake warning system of Britain should be able to detect a forthcoming quake and announce it several hours before it takes place. This would allow time for people to evacuate and reduce damage to the minimum. It can be inferred from the passage that England is rarely hit by high magnitude earthquakes.（）
经济体制改革的核心问题是处理好什么关系？
土地登记代理人在提交土地登记所需资料的同时，还应提交（），作为证实土地登记代理的合法性。
肠道菌科H抗原为（）。
根据变压器在电力系统中传输功率的方向，我们规定变压器接受功率一侧的绕组为一次绕组，一次绕组的作用相当于用电设备，其额定电压与网络的额定电压()。
凡士林又称软石蜡，有黄、白两种，后者经漂白而成。（）
《高层民用建筑设计防火规范》规定，二类高层建筑自备发电设备的切换要求是（）
呼吸急促、声高断续、喉间有哮鸣音的是（）情绪抑郁时不自觉地发出长吁或短叹声的是（）
眼超声可应用于诊断：①视网膜、脉络膜脱离；②眼内出血、异物；③眼内和眶内肿瘤；④眼肌异常（）