计算机系统地线汇集板宜采用600mm×200mm×20mm的（）制作。
A.铝板
B.铜板制作
C.不锈钢板
参考答案：B
Mark wants to buy a particular painting. He makes his request known to an art dealer who sells him the painting, providing him with a certificate guaranteeing the authenticity of the painting. Several months later, Mark has the painting valued and he is informed that the painting is a fake.Required:Advise Mark whether he may take action against the art dealer to invalidate the contract of purchase of the painting. (10 marks)
阅读分析材料，回答下列问题。
材料一：读“甲乙两国水系图”
甲国运河众多，大多是在1760到1840之间建造的，在修造铁路之前，担负繁重的运输任务，被称为甲国“工业革命的催化剂”。而乙国运河则寥寥无几。
（1）据图说出甲、乙两国的河流水系的异同点。
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（2）请从自然环境特点和社会经济发展角度分析甲乙两国运河长度差异产生的主要原因。
