春秋战国时期，对促进民族融合起直接作用的因素是（）。
A. 兼并战争
B. 铁器的使用
C. 各国变法
D. 商业兴盛
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为什么长期停车后，分子筛纯化器净化空气的效果显著降低？
NVH试验设置中，采样数1024，分析率3200，则频率分辨率为（）。
A. 3.125
B. 6.25
C. 0.32
D. 0.16
Which two statements are true about Oracle Real Applications Insight ？（）
A. it provides enhanced visibility across the entire application infrastructure
B. it provides a set of management tools that enable automation of configuraion
C. it significantly increases the performance of Web-based applications with no code change
D. it dramatically reduces costs associated with diagnostics， configuration， and deployment on production servers&e
Which of the following statements is TRUE regarding automatic identification systems (AIS) ?（）
A. The master may，at his/her discretion，turn off the AIS if he/she believes that it may compromise the safety or security of the vessel
B. Under no circumstances shall AIS be turned off while underway as this could endanger the vessel and those around her
C. AIS is always required to be operating if the vessel is in or in the vicinity of a VTS area
D. AIS is always required to be operating if the vessel is within 100 nautical miles of the coastline
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