保护生物多样性最为有效的措施是（　　）

如图所示，在研究磁场对电流作用的实验装置中，导体棒ab不可能选用下列哪种材料制成（　　）

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                                                                                                                                  春山夜月
                                                                                                                                  唐·于良史
                                                                                                                 春山多胜事，赏玩夜忘归。
                                                                                                                 掬水月在手，弄花香满衣。
                                                                                                                 兴来无远近，欲去惜芳菲。
                                                                                                                 南望鸣钟处，楼台深翠微。