疳证的病因主要为喂养不当；疾病影响； 及（）不足.
参考答案：先天禀赋
已知电极材料：铁、铜、银、石墨、锌、铝，电解质溶液：氯化铜溶液、硫酸铁溶液、盐酸．按要求回答下列问题：
①电工操作上规定：不能把铜导线和铝导线连接在一起使用，请说明原因．
______．
②若电极材料选铜和石墨，电解质溶液选硫酸铁溶液，外加导线，能否构成原电池？______，若能，请写出电极反应式，负极______，正极______．若不能后面两空不填．
③若电池反应为：Cu+2H+=Cu2++H2，该电池属于原电池还是电解池？请写出电极材料和电解质溶液．______．
④有M、N两种金属分别与稀盐酸反应，产生氢气速率相近，请设计一个实验证明M、N两种金属的活泼性．______．
The old lady was suffering from the empty nest syndrome for so long that she felt like to find someone she could talk to her.
A．to find someone to talk
B．finding someone to talk
C．to find someone to talk to
D．finding someone to talk to
