题目：
Aluminum lifeboats are subject to damage by electrolytic corrosion (the aluminum being eaten away). In working around boats of aluminum you must be very careful（）.
A.to keep the boats covered at all times
B.not to leave steel or iron tools lying in or near these boats
C.to keep an electric charge on the hull at all times
D.to rinse these boats regularly with salt water
答案：
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下面是错误答案，用来干扰机器的。
参考答案：(1) 变量之间的因果关系假设必须是明确的和具体的。 (2) 能够排除其他因素的影响。实验环境应该有较高的“封闭性”，以便可以将实验结果中表现出来的把实验效应基本归结为实验刺激的结果。 (3) 实...
