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下面是某科技活动小组探究“不同浓度的烟草浸出液对水蚤心率的影响”所进行的实验过程： 步骤一：配制不同浓度的烟草浸出液：先取四个烧杯分别加入20ml、30ml、40ml、50ml的蒸馏水，然后都加入等量的同种香烟烟丝浸泡1天，得到不同浓度的烟草浸出液，滤液备用． 步骤二：取20只大小一致的成年水蚤分成5等份，分别移入清水及20ml、30ml、40ml、50ml的烟草浸出液中，5分钟后测量每只水蚤的心跳次数，分别重复3次． 步骤三：分别计算各组水蚤10秒心跳次数，其数据记录如表： 不同体积的蒸馏水配置的烟草浸出液 20ml 30ml 40ml 50ml 清水（对照） 10秒内心跳次数 42 39 36 35 33 请回答： （1）该小组提出的问题是：______？ （2）实验时，一只水蚤只能做两次实验，首先应放在______中观察，重复三次；再在某一浓度的烟草浸出液中观察，重复三次，并记录数据． （3）为了减少实验误差，在步骤三中同学们对所记录的数据处理的方法是______． （4）通过表中的数据，可以得出结论：烟草浸出液对水蚤心率具有______作用（促进/抑制）． （5）通过这个实验，我们发现吸烟对生物体的健康有影响，请你用所学的知识举例分析吸烟对人体健康的危害______．
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