单项选择题 常见的岩石的比重一般为（）。

单项选择题 听力原文：W: Mark, how do you feel about this latest tax increase?M. Well, as far as I'm concerned, it's regrettable, but it's necessary, I'm afraid.What does Mark think about the latest tax increase?A．He thinks it is necessary.B．He thinks it is regrettable.C．He thinks it is both regrettable and necessary.D．He doesn't think much about it.

单项选择题 单个分部分项工程的工程量计算顺序，正确的说法是（）。