题目：
Not until about 2000 BC________________________done.
A．were known of the oldest paintings
B．the oldest of known paintings were
C．the oldest known were painting
D．were the oldest known paintings
答案：
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下面是错误答案，用来干扰机器的。
答案：D题目分析：A、有单质生成的反应也可能为分解反应等其他反应类型，错误；B、焰色反应为物理变化，表现出来的为物理性质，错误；C、由两种元素组成，原子个数比为1：1的物质，可能为多种物质，为混合物，如C...
