| To fight a noise by making more noise
sounds strange, but that’s exactly what motor engineers are doing in Germany and
some other countries. Car makers’ research and development laboratories have already proved that mixing more noise with the help of loudspeakers can reduce the unwanted noise. Physicists have known about the technique for a long time. Sound is made up of pressure waves in the air. If two sound waves of the same frequency (频率) mix so that the highest point of one wave happens at the same time as the lowest point of the other wave, the result is no sound. Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle (周期), we can kill the unwanted noise. Using this technique many carmakers are racing to develop noise-killing systems (系统) both inside and outside the cars. Anothe A. make a car lighter B. make a car quieter C. reduce the cost of a silencer D. improve the performance of a silencer [多选题]《中华人民共和国证券投资基金法》规定，属于申请取得基金托管资格应具备的条件是（）。
A.具有安全保管基金财产的条件 B.有安全高效的清算、交割系统 C.净资产和资本充足率符合有关规定 D.设有专门的基金托管部门 [单项选择]（）是指实现企业全部或主要贸易活动的电子化。
A. 电子商务 B. 网络营销 C. ERP D. CRM [单选题]动车组无停放制动装置或在坡度为（）以上的区间无动力停留时，由司机通知随车机械师进行防溜，防溜时使用止轮器牢靠固定。
A.2.5‰ B.6‰ C.12‰ D.20‰ [单选题]
（ ）仪表的灵敏度和精确度较高，多用来制作携带式电压表和电流表。 A.电磁式 B.磁电式 C.电动式 [单选题]广告经营者.发布者设计.制作.发布关系消费者生命健康商品或者服务的虚假广告,造成消费者损害的,应当与提供该商品或者服务的经营者承担()责任。
A.全部 B.部分 C.连带 [单选题]带电灭火时,如用二氧化碳灭火器的机体和喷嘴距10kV以下高压带电体不得小于（ ）米。
A.0.4 B.0.7 C.1.0 [单选题]不属于地方病的为( )
A.氟病 B.克山病 C.大骨节病 D.痛痛病 E.克汀病 [单选题]混凝土中水的用量与水泥用量的重量比值称为（）。
A.水泥标号 B.水灰比 C.混凝土的标号 我来回答: 提交
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